diff --git a/.github/workflows/release-drafter.yml b/.github/workflows/release-drafter.yml
new file mode 100644
index 00000000..9d39e165
--- /dev/null
+++ b/.github/workflows/release-drafter.yml
@@ -0,0 +1,19 @@
+name: Release Drafter
+
+on:
+  push:
+    # branches to consider in the event; optional, defaults to all
+    branches:
+      - master
+
+jobs:
+  update_release_draft:
+    runs-on: ubuntu-latest
+    steps:
+      # Drafts your next Release notes as Pull Requests are merged into "master"
+      - uses: release-drafter/release-drafter@v5
+        # with:
+          # (Optional) specify config name to use, relative to .github/. Default: release-drafter.yml
+          # config-name: my-config.yml
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.github/workflows/stale.yml b/.github/workflows/stale.yml
new file mode 100644
index 00000000..7edec9eb
--- /dev/null
+++ b/.github/workflows/stale.yml
@@ -0,0 +1,19 @@
+name: Mark stale issues and pull requests
+
+on:
+  schedule:
+  - cron: "0 0 * * *"
+
+jobs:
+  stale:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/stale@v1
+      with:
+        repo-token: ${{ secrets.GITHUB_TOKEN }}
+        stale-issue-message: 'This issue has been marked as stale and will be automatically closed.'
+        stale-pr-message: 'This pull request has been marked as stale and will be automatically closed.'
+        stale-issue-label: 'no-issue-activity'
+        stale-pr-label: 'no-pr-activity'
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 00000000..b7b46a72
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,71 @@
+name: Test workflow
+
+on: [push, pull_request]
+
+jobs:
+  test:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest]
+        ruby:
+          - '2.5'
+          - '2.6'
+          - '2.7'
+          - '3.0'
+          - '3.1'
+        rails:
+          - '~> 4.1'
+          - '~> 5.2'
+          - '~> 6.0.0'
+          - '~> 6.1'
+          - '~> 7.0.0'
+        exclude:
+          - ruby: '2.5'
+            rails: '~> 7.0.0'
+          - ruby: '2.6'
+            rails: '~> 7.0.0'
+          - ruby: '2.7'
+            rails: '~> 4.1'
+          - ruby: '3.0'
+            rails: '~> 4.1'
+          - ruby: '3.0'
+            rails: '~> 5.2'
+          - ruby: '3.1'
+            rails: '~> 4.1'
+          - ruby: '3.1'
+            rails: '~> 5.2'
+          - ruby: '3.1'
+            rails: '~> 6.0.0'
+    runs-on: ${{ matrix.os }}
+    env:
+      RAILS_VERSION: ${{ matrix.rails }}
+    steps:
+    - uses: actions/checkout@v2
+    - uses: ruby/setup-ruby@v1
+      # rubygems-update's latest is no longer compatible with ruby 2.5, so conditionally run ruby-setup setting the
+      # rubygem version the most recent valid version for 2.5:
+      # https://rubygems.org/gems/rubygems-update/versions/3.3.26
+      if: ${{ matrix.ruby == '2.5' }}
+      with:
+        ruby-version: ${{ matrix.ruby }}
+        rubygems: 3.3.26
+        bundler: latest
+        bundler-cache: true
+    - uses: ruby/setup-ruby@v1
+      # otherwise, we can use rubygems latest
+      if: ${{ matrix.ruby != '2.5' }}
+      with:
+        ruby-version: ${{ matrix.ruby }}
+        rubygems: latest
+        bundler: latest
+        bundler-cache: true
+
+    - name: Setup wkhtmltopdf
+      run: |
+        sudo apt-get install -y xfonts-base xfonts-75dpi
+        wget https://github.com/wkhtmltopdf/packaging/releases/download/0.12.6-1/wkhtmltox_0.12.6-1.bionic_amd64.deb
+        sudo dpkg -i wkhtmltox_0.12.6-1.bionic_amd64.deb
+
+    - name: Run tests
+      run: bundle exec rake
diff --git a/.ruby-version b/.ruby-version
index f33eb12f..d48d3702 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-ruby-2.0.0
+2.6.9
diff --git a/.travis.yml b/.travis.yml
index 16529a0f..a859ba9d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,16 +1,46 @@
+language: ruby
+
 rvm:
-- 1.9.2
-- 1.9.3
-- 2.0
-- 2.1
+- 2.5
+- 2.6
+- 2.7
+- 3.0
+- 3.1
+
+env:
+  matrix:
+    - RAILS_VERSION="~> 4.1"
+    - RAILS_VERSION="~> 5.2"
+    - RAILS_VERSION="~> 6.0.0"
+    - RAILS_VERSION="~> 6.1"
+    - RAILS_VERSION="~> 7.0.0"
+
+jobs:
+  exclude:
+  - rvm: 2.5
+    env: RAILS_VERSION="~> 7.0.0"
+  - rvm: 2.6
+    env: RAILS_VERSION="~> 7.0.0"
+  - rvm: 2.7
+    env: RAILS_VERSION="~> 4.1"
+  - rvm: 3.0
+    env: RAILS_VERSION="~> 4.1"
+  - rvm: 3.0
+    env: RAILS_VERSION="~> 5.2"
+  - rvm: 3.1
+    env: RAILS_VERSION="~> 4.1"
+  - rvm: 3.1
+    env: RAILS_VERSION="~> 5.2"
+  - rvm: 3.1
+    env: RAILS_VERSION="~> 6.0.0"
+
+cache: bundler
 
 before_install:
   - gem update --system
   - gem update bundler
 
 before_script:
-  - "export DISPLAY=:99.0"
-  - "sh -e /etc/init.d/xvfb start"
   - "sudo apt-get -qq -y install fontconfig libxrender1"
-  - "wget http://download.gna.org/wkhtmltopdf/0.12/0.12.1/wkhtmltox-0.12.1_linux-precise-amd64.deb"
-  - "sudo dpkg -i wkhtmltox-0.12.1_linux-precise-amd64.deb"
+  - "wget https://github.com/wkhtmltopdf/wkhtmltopdf/releases/download/0.12.5/wkhtmltox_0.12.5-1.xenial_amd64.deb"
+  - "sudo apt-get install ./wkhtmltox_0.12.5-1.xenial_amd64.deb"
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 919b961c..a46c04b7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,72 @@
+2023-02-27
+=================
+  * Bump to 0.8.7.3
+  * Allow passing a `Pathname` object to the `path` argument by @yujideveloper in https://github.com/pdfkit/pdfkit/pull/522
+  * Update repeatable options by @mguidetti in https://github.com/pdfkit/pdfkit/pull/524
+
+2022-10-18
+=================
+  * Bump to 0.8.7.2
+  * Call IO.popen with an Array of command arguments (#519)
+
+2022-10-17
+=================
+  * Bump to 0.8.7.1
+  * Support non-lower-case Content-Type header provided by app (#516)
+
+2022-10-02
+=================
+  * Bump to 0.8.7
+  * Lowercase the header names for rack 3 changes (#511)
+  * Partially escaped URLs should be escaped (#509)
+
+2022-04-11
+=================
+  * Bump to 0.8.6
+  * Update ruby and rails versions
+
+2021-01-23
+=================
+  * Bump to 0.8.5
+  * Make `PDFKit::VERSION` public (#484) 
+  * Fix to render stylesheets as html safe string on Rails 6 (#483)
+      * Adds support for Rails 6
+
+2020-08-16
+=================
+  * Bump to 0.8.4.3.2
+  * Reduce scope of middleware exception handling (#476)
+
+2020-07-05
+=================
+  * Bump to 0.8.4.3.1
+  * Don't override request level Content-Disposition header if it exists (#466)
+  * Update rake (#471)
+  * Add missing require statements for tempfile (#467)
+  * Only grab last line of bundle exec which output (#464)
+  * Return 500 status when an exception is caught in middleware (#469)
+  * Update Travis CI URL for wkhtmltopf (#473)
+  
+2020-04-01
+=================
+  * Bump to 0.8.4.2
+  * Improve path detection feedback (#460)
+  * Fix typos (#444)
+  * Update readme (#439)
+  
+2019-02-22
+=================
+  * Bump to 0.8.4.1
+  * Make PDFkit threadsafe (#377)
+  * Update activesupport (#434)
+
+2019-02-21
+=================
+  * Bump to 0.8.4
+  * Removed support for Ruby < 2.2
+  * Xvfb support (#277)
+  * Remove 'config.protocol' from the README (#389)
+
 2015-08-26
 =================
   * Bump to 0.8.2
diff --git a/Gemfile b/Gemfile
index 12a4e43d..5b623bd2 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,7 +1,7 @@
 source 'https://rubygems.org'
 
 group :test do
-  gem 'activesupport', '~> 3.0'
+  gem 'activesupport', ENV['RAILS_VERSION'] || '~> 4.1'
   gem 'simplecov', require: false
 end
 
diff --git a/README.md b/README.md
index 0ebaf683..bfa3799a 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,11 @@
 
 Create PDFs using plain old HTML+CSS. Uses [wkhtmltopdf](http://github.com/antialize/wkhtmltopdf) on the back-end which renders HTML using Webkit.
 
+## Supported versions
+
+- Ruby 2.5, 2.6, 2.7, 3.0, 3.1
+- Rails 4.2, 5.2, 6.0, 6.1, 7.0
+
 ## Install
 
 ### PDFKit
@@ -14,7 +19,7 @@ gem install pdfkit
 
     <https://github.com/pdfkit/pdfkit/wiki/Installing-WKHTMLTOPDF>
 
-2.  Try using the `wkhtmltopdf-binary` gem (mac + linux i386)
+2.  Try using the `wkhtmltopdf-binary-edge` gem (mac + linux i386)
 ```
 gem install wkhtmltopdf-binary
 ```
@@ -34,7 +39,7 @@ pdf = kit.to_pdf
 file = kit.to_file('/path/to/save/pdf')
 
 # PDFKit.new can optionally accept a URL or a File.
-# Stylesheets can not be added when source is provided as a URL of File.
+# Stylesheets can not be added when source is provided as a URL or File.
 kit = PDFKit.new('http://google.com')
 kit = PDFKit.new(File.new('/path/to/html'))
 
@@ -58,7 +63,7 @@ PDFKit.new(html, protocol: 'https').to_file
 ```
 
 ### Using cookies in scraping
-If you want to pass a cookie to cookie to pdfkit to scrape a website, you can
+If you want to pass a cookie to pdfkit to scrape a website, you can
 pass it in a hash:
 ```ruby
 kit = PDFKit.new(url, cookie: {cookie_name: :cookie_value})
@@ -76,7 +81,6 @@ PDFKit.configure do |config|
   }
   # Use only if your external hostname is unavailable on the server.
   config.root_url = "http://localhost"
-  config.protocol = 'http'
   config.verbose = false
 end
 ```
@@ -117,6 +121,13 @@ config.middleware.use PDFKit::Middleware, {}, :except => [%r[^/prawn], %r[^/secr
 # conditions can be strings (either one or an array)
 config.middleware.use PDFKit::Middleware, {}, :except => ['/secret']
 ```
+**With conditions to force download**
+```ruby
+# force download with attachment disposition
+config.middleware.use PDFKit::Middleware, {}, :disposition => 'attachment'
+# conditions can force a filename
+config.middleware.use PDFKit::Middleware, {}, :disposition => 'attachment; filename=report.pdf'
+```
 **Saving the generated .pdf to disk**
 
 Setting the `PDFKit-save-pdf` header will cause PDFKit to write the generated .pdf to the file indicated by the value of the header.
@@ -126,7 +137,7 @@ For example:
 headers['PDFKit-save-pdf'] = 'path/to/saved.pdf'
 ```
 
-Will cause the .pdf to be saved to `path/to/saved.pdf` in addition to being sent back to the client.  If the path is not writable/non-existant the write will fail silently.  The `PDFKit-save-pdf` header is never sent back to the client.
+Will cause the .pdf to be saved to `path/to/saved.pdf` in addition to being sent back to the client.  If the path is not writable/non-existent the write will fail silently.  The `PDFKit-save-pdf` header is never sent back to the client.
 
 ## Troubleshooting
 
@@ -141,13 +152,13 @@ Will cause the .pdf to be saved to `path/to/saved.pdf` in addition to being sent
    around this issue you may want to run a server with multiple workers
    like Passenger or try to embed your resources within your HTML to
    avoid extra HTTP requests.
-   
+
    Example solution (rails / bundler), add unicorn to the development
    group in your Gemfile `gem 'unicorn'` then run `bundle`. Next, add a
    file `config/unicorn.conf` with
-   
+
         worker_processes 3
-   
+
    Then to run the app `unicorn_rails -c config/unicorn.conf` (from rails_root)
 
 *  **Resources aren't included in the PDF:** Images, CSS, or JavaScript
@@ -161,7 +172,7 @@ Will cause the .pdf to be saved to `path/to/saved.pdf` in addition to being sent
    asset host.
 
 *  **Mangled output in the browser:** Be sure that your HTTP response
-   headers specify "Content-Type: application/pdf"
+   headers specify "content-type: application/pdf"
 
 ## Note on Patches/Pull Requests
 
diff --git a/lib/pdfkit.rb b/lib/pdfkit.rb
index 908e266f..1ea91906 100644
--- a/lib/pdfkit.rb
+++ b/lib/pdfkit.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'pdfkit/source'
 require 'pdfkit/pdfkit'
 require 'pdfkit/middleware'
@@ -5,3 +7,4 @@
 require 'pdfkit/os'
 require 'pdfkit/configuration'
 require 'pdfkit/wkhtmltopdf'
+require 'pdfkit/version'
diff --git a/lib/pdfkit/configuration.rb b/lib/pdfkit/configuration.rb
index 28172147..6eaa7e0e 100644
--- a/lib/pdfkit/configuration.rb
+++ b/lib/pdfkit/configuration.rb
@@ -1,10 +1,14 @@
+# frozen_string_literal: true
+
 class PDFKit
   class Configuration
-    attr_accessor :meta_tag_prefix, :default_options, :root_url
-    attr_writer :verbose
+    attr_accessor :meta_tag_prefix, :root_url
+    attr_writer :use_xvfb, :verbose
+    attr_reader :default_options
 
     def initialize
       @verbose         = false
+      @use_xvfb        = false
       @meta_tag_prefix = 'pdfkit-'
       @default_options = {
         :disable_smart_shrinking => false,
@@ -23,18 +27,31 @@ def wkhtmltopdf
     end
 
     def default_wkhtmltopdf
-      @default_command_path ||= (defined?(Bundler::GemfileError) && File.exists?('Gemfile') ? `bundle exec which wkhtmltopdf` : `which wkhtmltopdf`).chomp
+      return @default_command_path if @default_command_path
+      if defined?(Bundler::GemfileError) && File.exist?('Gemfile')
+        @default_command_path = `bundle exec which wkhtmltopdf`.chomp.lines.last
+      end
+      @default_command_path = `which wkhtmltopdf`.chomp if @default_command_path.nil? || @default_command_path.empty?
+      @default_command_path
     end
 
     def wkhtmltopdf=(path)
       if File.exist?(path)
         @wkhtmltopdf = path
       else
-        warn "No executable found at #{path}. Will fall back to #{default_wkhtmltopdf}" unless File.exist?(path)
+        warn "No executable found at #{path}. Will fall back to #{default_wkhtmltopdf}"
         @wkhtmltopdf = default_wkhtmltopdf
       end
     end
 
+    def executable
+      using_xvfb? ? ['xvfb-run', wkhtmltopdf] : wkhtmltopdf
+    end
+
+    def using_xvfb?
+      @use_xvfb
+    end
+
     def quiet?
       !@verbose
     end
@@ -42,6 +59,10 @@ def quiet?
     def verbose?
       @verbose
     end
+
+    def default_options=(options)
+      @default_options.merge!(options)
+    end
   end
 
   class << self
@@ -54,6 +75,7 @@ class << self
   # @example
   #   PDFKit.configure do |config|
   #     config.wkhtmltopdf = '/usr/bin/wkhtmltopdf'
+  #     config.use_xvfb    = true
   #     config.verbose     = true
   #   end
 
diff --git a/lib/pdfkit/html_preprocessor.rb b/lib/pdfkit/html_preprocessor.rb
index c402b1ab..611613bc 100644
--- a/lib/pdfkit/html_preprocessor.rb
+++ b/lib/pdfkit/html_preprocessor.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PDFKit
   module HTMLPreprocessor
 
diff --git a/lib/pdfkit/middleware.rb b/lib/pdfkit/middleware.rb
index 0d794382..c397e10a 100644
--- a/lib/pdfkit/middleware.rb
+++ b/lib/pdfkit/middleware.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PDFKit
   class Middleware
     def initialize(app, options = {}, conditions = {})
@@ -9,35 +11,51 @@ def initialize(app, options = {}, conditions = {})
     end
 
     def call(env)
+      dup._call(env)
+    end
+
+    def _call(env)
       @request    = Rack::Request.new(env)
       @render_pdf = false
 
       set_request_to_render_as_pdf(env) if render_as_pdf?
       status, headers, response = @app.call(env)
 
-      if rendering_pdf? && headers['Content-Type'] =~ /text\/html|application\/xhtml\+xml/
-        body = response.respond_to?(:body) ? response.body : response.join
-        body = body.join if body.is_a?(Array)
-
-        root_url = root_url(env)
-        protocol = protocol(env)
-        options = @options.merge(root_url: root_url, protocol: protocol)
-        body = PDFKit.new(body, options).to_pdf
-        response = [body]
-
-        if headers['PDFKit-save-pdf']
-          File.open(headers['PDFKit-save-pdf'], 'wb') { |file| file.write(body) } rescue nil
-          headers.delete('PDFKit-save-pdf')
-        end
-
-        unless @caching
-          # Do not cache PDFs
-          headers.delete('ETag')
-          headers.delete('Cache-Control')
+      begin
+        content_type_header = headers.has_key?('Content-Type') ? 'Content-Type' : 'content-type'
+        if rendering_pdf? && headers[content_type_header] =~ /text\/html|application\/xhtml\+xml/
+          body = response.respond_to?(:body) ? response.body : response.join
+          body = body.join if body.is_a?(Array)
+
+          root_url = root_url(env)
+          protocol = protocol(env)
+          options = @options.merge(root_url: root_url, protocol: protocol)
+
+          if headers['PDFKit-javascript-delay']
+            options.merge!(javascript_delay: headers.delete('PDFKit-javascript-delay').to_i)
+          end
+
+          body = PDFKit.new(body, options).to_pdf
+          response = [body]
+
+          if headers['PDFKit-save-pdf']
+            File.open(headers['PDFKit-save-pdf'], 'wb') { |file| file.write(body) } rescue nil
+            headers.delete('PDFKit-save-pdf')
+          end
+
+          unless @caching
+            # Do not cache PDFs
+            headers.delete('etag')
+            headers.delete('cache-control')
+          end
+
+          headers['content-length'] = (body.respond_to?(:bytesize) ? body.bytesize : body.size).to_s
+          headers[content_type_header]   = 'application/pdf'
+          headers['content-disposition'] ||= @conditions[:disposition] || 'inline'
         end
-
-        headers['Content-Length'] = (body.respond_to?(:bytesize) ? body.bytesize : body.size).to_s
-        headers['Content-Type']   = 'application/pdf'
+      rescue StandardError => e
+        status = 500
+        response = [e.message]
       end
 
       [status, headers, response]
diff --git a/lib/pdfkit/os.rb b/lib/pdfkit/os.rb
index 12721c6c..e05b1dd1 100644
--- a/lib/pdfkit/os.rb
+++ b/lib/pdfkit/os.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rbconfig'
 
 class PDFKit
diff --git a/lib/pdfkit/pdfkit.rb b/lib/pdfkit/pdfkit.rb
index 3ebf027f..9ef7ad4b 100644
--- a/lib/pdfkit/pdfkit.rb
+++ b/lib/pdfkit/pdfkit.rb
@@ -1,20 +1,31 @@
+# frozen_string_literal: true
+
 require 'shellwords'
+require 'tempfile'
 
 class PDFKit
-  class NoExecutableError < StandardError
+  class Error < StandardError; end
+
+  class NoExecutableError < Error
     def initialize
-      msg  = "No wkhtmltopdf executable found at #{PDFKit.configuration.wkhtmltopdf}\n"
-      msg << ">> Please install wkhtmltopdf - https://github.com/pdfkit/PDFKit/wiki/Installing-WKHTMLTOPDF"
+      msg = "No wkhtmltopdf executable found at #{PDFKit.configuration.wkhtmltopdf}\n" \
+            ">> Please install wkhtmltopdf - https://github.com/pdfkit/PDFKit/wiki/Installing-WKHTMLTOPDF"
       super(msg)
     end
   end
 
-  class ImproperSourceError < StandardError
+  class ImproperSourceError < Error
     def initialize(msg)
       super("Improper Source: #{msg}")
     end
   end
 
+  class ImproperWkhtmltopdfExitStatus < Error
+    def initialize(invoke)
+      super("Command failed (exitstatus=#{$?.exitstatus}): #{invoke}")
+    end
+  end
+
   attr_accessor :source, :stylesheets
   attr_reader :renderer
 
@@ -31,20 +42,15 @@ def initialize(url_file_or_html, options = {})
     @renderer = WkHTMLtoPDF.new options
     @renderer.normalize_options
 
-    raise NoExecutableError.new unless File.exists?(PDFKit.configuration.wkhtmltopdf)
+    raise NoExecutableError unless File.exist?(PDFKit.configuration.wkhtmltopdf)
   end
 
   def command(path = nil)
-    args = @renderer.options_for_command
-    shell_escaped_command = [executable, OS::shell_escape_for_os(args)].join ' '
-
-    # In order to allow for URL parameters (e.g. https://www.google.com/search?q=pdfkit) we do
-    # not escape the source. The user is responsible for ensuring that no vulnerabilities exist
-    # in the source. Please see https://github.com/pdfkit/pdfkit/issues/164.
-    input_for_command = @source.to_input_for_command
-    output_for_command = path ? Shellwords.shellescape(path) : '-'
-
-    "#{shell_escaped_command} #{input_for_command} #{output_for_command}"
+    args = [*executable]
+    args.concat(@renderer.options_for_command)
+    args << @source.to_input_for_command
+    args << (path ? path.to_s : '-')
+    args
   end
 
   def options
@@ -53,7 +59,7 @@ def options
   end
 
   def executable
-    PDFKit.configuration.wkhtmltopdf
+    PDFKit.configuration.executable
   end
 
   def to_pdf(path=nil)
@@ -70,7 +76,7 @@ def to_pdf(path=nil)
 
     # $? is thread safe per
     # http://stackoverflow.com/questions/2164887/thread-safe-external-process-in-ruby-plus-checking-exitstatus
-    raise "command failed (exitstatus=#{$?.exitstatus}): #{invoke}" if empty_result?(path, result) or !successful?($?)
+    raise ImproperWkhtmltopdfExitStatus, invoke if empty_result?(path, result) || !successful?($?)
     return result
   end
 
@@ -83,7 +89,7 @@ def to_file(path)
 
   def find_options_in_meta(content)
     # Read file if content is a File
-    content = content.read if content.is_a?(File)
+    content = content.read if content.is_a?(File) || content.is_a?(Tempfile)
 
     found = {}
     content.scan(/<meta [^>]*>/) do |meta|
@@ -105,7 +111,9 @@ def find_options_in_meta(content)
   end
 
   def style_tag_for(stylesheet)
-    "<style>#{File.read(stylesheet)}</style>"
+    style = "<style>#{File.read(stylesheet)}</style>"
+    style = style.html_safe if style.respond_to?(:html_safe)
+    style
   end
 
   def preprocess_html
@@ -116,11 +124,13 @@ def preprocess_html
   end
 
   def append_stylesheets
-    raise ImproperSourceError.new('Stylesheets may only be added to an HTML source') if stylesheets.any? && !@source.html?
+    raise ImproperSourceError, 'Stylesheets may only be added to an HTML source' if stylesheets.any? && !@source.html?
 
     stylesheets.each do |stylesheet|
       if @source.to_s.match(/<\/head>/)
-        @source = Source.new(@source.to_s.gsub(/(<\/head>)/) {|s| style_tag_for(stylesheet) + s })
+        @source = Source.new(@source.to_s.gsub(/(<\/head>)/) {|s|
+          style_tag_for(stylesheet) + (s.respond_to?(:html_safe) ? s.html_safe : s)
+        })
       else
         @source.to_s.insert(0, style_tag_for(stylesheet))
       end
diff --git a/lib/pdfkit/source.rb b/lib/pdfkit/source.rb
index de1d2314..5238acca 100644
--- a/lib/pdfkit/source.rb
+++ b/lib/pdfkit/source.rb
@@ -1,3 +1,6 @@
+# frozen_string_literal: true
+
+require 'tempfile'
 require 'uri'
 
 class PDFKit
@@ -6,6 +9,8 @@ class Source
 
     def initialize(url_file_or_html)
       @source = url_file_or_html
+      # @source is assumed to be modifiable, so make sure it is.
+      @source = @source.dup if @source.is_a?(String) && @source.frozen?
     end
 
     def url?
@@ -13,7 +18,7 @@ def url?
     end
 
     def file?
-      @is_file ||= @source.kind_of?(File)
+      @is_file ||= @source.kind_of?(File) || @source.kind_of?(Tempfile)
     end
 
     def html?
@@ -24,7 +29,7 @@ def to_input_for_command
       if file?
         @source.path
       elsif url?
-        %{"#{shell_safe_url}"}
+        escaped_url
       else
         SOURCE_FROM_STDIN
       end
@@ -36,12 +41,12 @@ def to_s
 
     private
 
-    def shell_safe_url
-      url_needs_escaping? ? URI::escape(@source) : @source
+    def escaped_url
+      url_needs_escaping? ? URI::DEFAULT_PARSER.escape(@source) : @source
     end
 
     def url_needs_escaping?
-      URI::decode(@source) == @source
+      URI::DEFAULT_PARSER.escape(URI::DEFAULT_PARSER.unescape(@source)) != @source
     end
   end
 end
diff --git a/lib/pdfkit/version.rb b/lib/pdfkit/version.rb
index 9d8bdd39..f82a00e2 100644
--- a/lib/pdfkit/version.rb
+++ b/lib/pdfkit/version.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PDFKit
-  VERSION = "0.8.2"
+  VERSION = '0.8.7.3'
 end
diff --git a/lib/pdfkit/wkhtmltopdf.rb b/lib/pdfkit/wkhtmltopdf.rb
index 86220ba2..e72f9238 100644
--- a/lib/pdfkit/wkhtmltopdf.rb
+++ b/lib/pdfkit/wkhtmltopdf.rb
@@ -1,10 +1,12 @@
+# frozen_string_literal: true
+
 class PDFKit
   class WkHTMLtoPDF
     attr_reader :options
-    # Pulled from:
-    # https://github.com/wkhtmltopdf/wkhtmltopdf/blob/ebf9b6cfc4c58a31349fb94c568b254fac37b3d3/README_WKHTMLTOIMAGE#L27
-    REPEATABLE_OPTIONS = %w[--allow --cookie --custom-header --post --post-file --run-script]
-    SPECIAL_OPTIONS = %w[cover toc]
+    # Pulled from: 
+    # https://github.com/wkhtmltopdf/wkhtmltopdf/blob/6a57c1449797d6cb915921fb747f3ac36199241f/docs/usage/wkhtmltopdf.txt#L104
+    REPEATABLE_OPTIONS = %w[--allow --bypass-proxy-for --cookie --custom-header --post --post-file --run-script --replace].freeze
+    SPECIAL_OPTIONS = %w[cover toc].freeze
 
     def initialize(options)
       @options = options
@@ -62,7 +64,7 @@ def normalize_value(value)
       when Array
         value.flatten.collect{|x| x.to_s}
       else
-        (OS::host_is_windows? && value.to_s.index(' ')) ? "'#{ value.to_s }'" : value.to_s
+        value.to_s
       end
     end
   
diff --git a/pdfkit.gemspec b/pdfkit.gemspec
index 9ca668d2..d68270d3 100644
--- a/pdfkit.gemspec
+++ b/pdfkit.gemspec
@@ -13,21 +13,20 @@ Gem::Specification.new do |s|
   s.description = "Uses wkhtmltopdf to create PDFs using HTML"
   s.license     = "MIT"
 
-  s.rubyforge_project = "pdfkit"
-
   s.files         = `git ls-files`.split("\n")
   s.test_files    = `git ls-files -- {test,spec,features}/*`.split("\n")
   s.executables   = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) }
   s.require_paths = ["lib"]
 
+  s.required_ruby_version = ">= 2.5"
+
   s.requirements << "wkhtmltopdf"
 
   # Development Dependencies
-  s.add_development_dependency(%q<activesupport>, [">= 3.0.8"])
+  s.add_development_dependency(%q<activesupport>, [">= 4.1.11"])
   s.add_development_dependency(%q<mocha>, [">= 0.9.10"])
   s.add_development_dependency(%q<rack-test>, [">= 0.5.6"])
-  s.add_development_dependency(%q<i18n>, ["~>0.6.11"]) # Ruby 1.9.2 compatibility
-  s.add_development_dependency(%q<rake>, ["~>0.9.2"])
-  s.add_development_dependency(%q<rdoc>, ["~> 4.0.1"])
+  s.add_development_dependency(%q<rake>, [">= 12.3.3"])
+  s.add_development_dependency(%q<rdoc>, [">= 4.0.1"])
   s.add_development_dependency(%q<rspec>, ["~> 3.0"])
 end
diff --git a/spec/configuration_spec.rb b/spec/configuration_spec.rb
index 355085b6..a3c2b2b5 100644
--- a/spec/configuration_spec.rb
+++ b/spec/configuration_spec.rb
@@ -1,14 +1,75 @@
+# frozen_string_literal: true
+
 require 'spec_helper'
 
 describe PDFKit::Configuration do
   subject { PDFKit::Configuration.new }
   describe "#wkhtmltopdf" do
+    context "when explicitly configured" do
+      it "uses configured value and don't detect" do
+        expect(subject).not_to receive(:default_wkhtmltopdf)
+        subject.wkhtmltopdf = "./Gemfile" # Need a file which exists
+        expect(subject.wkhtmltopdf).to eq("./Gemfile")
+      end
+
+      it "falls back to detected binary if configured path doesn't exists" do
+        expect(subject).to receive(:default_wkhtmltopdf).twice.and_return("/bin/fallback")
+        expect(subject).to receive(:warn).with(/No executable found/)
+        subject.wkhtmltopdf = "./missing-file" # Need a file which doesn't exist
+        expect(subject.wkhtmltopdf).to eq("/bin/fallback")
+      end
+    end
+
     context "when not explicitly configured" do
-      it "detects the existance of bundler" do
-        # Test assumes bundler is installed in your test environment
-        expect(subject).to receive(:`).with('bundle exec which wkhtmltopdf').and_return('c:\windows\path.exe')
-        subject.wkhtmltopdf
+      context "when running inside bundler" do
+        # Simulate the presence of bundler even if it's not here
+        before { stub_const("Bundler::GemfileError", Class) }
+
+        it "detects the existance of bundler" do
+          expect(subject).to receive(:`).with('bundle exec which wkhtmltopdf').and_return("c:\\windows\\path.exe\n")
+          expect(subject.wkhtmltopdf).to eq('c:\windows\path.exe')
+        end
+
+        it "falls back if bundler path fails" do
+          # This happens when there is a wrong (buggy) version of bundler for example
+          expect(subject).to receive(:`).with('bundle exec which wkhtmltopdf').and_return("")
+          expect(subject).to receive(:`).with('which wkhtmltopdf').and_return("c:\\windows\\path.exe\n")
+          expect(subject.wkhtmltopdf).to eq('c:\windows\path.exe')
+        end
+
+        it "returns last line of 'bundle exec which' output" do
+          # Happens when the user does not have a HOME directory on their system and runs bundler < 2
+          expect(subject).to receive(:`).with('bundle exec which wkhtmltopdf').and_return(<<~EOT
+            `/home/myuser` is not a directory.
+            Bundler will use `/tmp/bundler/home/myuser' as your home directory temporarily.
+            /usr/bin/wkhtmltopdf
+          EOT
+          )
+          expect(subject.wkhtmltopdf).to eq('/usr/bin/wkhtmltopdf')
+        end
       end
+
+      context "when running without bundler" do
+        # Simulate the absence of bundler even if it's there
+        before { hide_const("Bundler::GemfileError") }
+
+        it "detects the existance of bundler" do
+          expect(subject).not_to receive(:`).with('bundle exec which wkhtmltopdf')
+          expect(subject).to receive(:`).with('which wkhtmltopdf').and_return('c:\windows\path.exe')
+          expect(subject.wkhtmltopdf).to eq('c:\windows\path.exe')
+        end
+      end
+    end
+  end
+
+  describe "#executable" do
+    it "returns wkhtmltopdf by default" do
+      expect(subject.executable).to eql subject.wkhtmltopdf
+    end
+
+    it "uses xvfb-run wrapper when option of using xvfb is configured" do
+      expect(subject).to receive(:using_xvfb?).and_return(true)
+      expect(subject.executable).to include 'xvfb-run'
     end
   end
 
@@ -29,6 +90,13 @@
       expect(subject.default_options[:quiet]).to eql false
       expect(subject.default_options[:is_awesome]).to eql true
     end
+
+    it "merges additional options with existing defaults" do
+      subject.default_options = { quiet: false, is_awesome: true }
+      expect(subject.default_options[:quiet]).to eql false
+      expect(subject.default_options[:is_awesome]).to eql true
+      expect(subject.default_options[:disable_smart_shrinking]).to eql false
+    end
   end
 
   describe "#root_url" do
@@ -53,6 +121,22 @@
     end
   end
 
+  describe "#using_xvfb?" do
+    it "can be configured to true" do
+      subject.use_xvfb = true
+      expect(subject.using_xvfb?).to eql true
+    end
+
+    it "defaults to false" do
+      expect(subject.using_xvfb?).to eql false
+    end
+
+    it "can be configured to false" do
+      subject.use_xvfb = false
+      expect(subject.using_xvfb?).to eql false
+    end
+  end
+
   describe "#verbose?" do
     it "can be configured to true" do
       subject.verbose = true
diff --git a/spec/html_preprocessor_spec.rb b/spec/html_preprocessor_spec.rb
index f57b393e..bfa0b794 100644
--- a/spec/html_preprocessor_spec.rb
+++ b/spec/html_preprocessor_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'spec_helper'
 
 describe PDFKit::HTMLPreprocessor do
diff --git a/spec/middleware_spec.rb b/spec/middleware_spec.rb
index fec6942c..72ced7e8 100644
--- a/spec/middleware_spec.rb
+++ b/spec/middleware_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'spec_helper'
 
 def app; Rack::Lint.new(@app); end
@@ -17,43 +19,72 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
 
 describe PDFKit::Middleware do
   let(:headers) do
-    {'Content-Type' => "text/html"}
+    {'content-type' => "text/html"}
   end
 
   describe "#call" do
+
+    describe 'threadsafety' do
+      before { mock_app }
+      it 'is threadsafe' do
+        n = 30
+        extensions = Array.new(n) { rand > 0.5 ? 'html' : 'pdf' }
+        actual_content_types = Hash.new
+
+        threads = (0...n).map { |i|
+          Thread.new do
+            resp = get("http://www.example.org/public/test.#{extensions[i]}")
+            actual_content_types[i] = resp.content_type
+          end
+        }
+
+        threads.each(&:join)
+
+        extensions.each_with_index do |extension, index|
+          result = actual_content_types[index]
+          case extension
+          when 'html', 'txt', 'csv'
+            expect(result).to eq("text/#{extension}")
+          when 'pdf'
+            expect(result).to eq('application/pdf')
+          end
+        end
+      end
+    end
+
     describe "caching" do
       let(:headers) do
         {
-          'Content-Type' => "text/html",
-          'ETag' => 'foo',
-          'Cache-Control' => 'max-age=2592000, public'
+          'content-type' => "text/html",
+          'etag' => 'foo',
+          'cache-control' => 'max-age=2592000, public'
         }
       end
 
       context "by default" do
         before { mock_app }
 
-        it "deletes ETag" do
+        it "deletes etag" do
           get 'http://www.example.org/public/test.pdf'
-          expect(last_response.headers["ETag"]).to be_nil
+          expect(last_response.headers["etag"]).to be_nil
         end
-        it "deletes Cache-Control" do
+        it "deletes cache-control" do
           get 'http://www.example.org/public/test.pdf'
-          expect(last_response.headers["Cache-Control"]).to be_nil
+          expect(last_response.headers["cache-control"]).to be_nil
         end
       end
 
       context "when on" do
         before { mock_app({}, :caching => true) }
 
-        it "preserves ETag" do
+        it "preserves etag" do
           get 'http://www.example.org/public/test.pdf'
-          expect(last_response.headers["ETag"]).not_to be_nil
+          expect(last_response.headers["etag"]).not_to be_nil
         end
 
-        it "preserves Cache-Control" do
+        it "preserves cache-control" do
           get 'http://www.example.org/public/test.pdf'
-          expect(last_response.headers["Cache-Control"]).not_to be_nil
+          expect(last_response.headers["cache-control"]).not_to be_nil
         end
       end
     end
@@ -68,7 +99,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             context "matching" do
               specify do
                 get 'http://www.example.org/public/test.pdf'
-                expect(last_response.headers["Content-Type"]).to eq("application/pdf")
+                expect(last_response.headers["content-type"]).to eq("application/pdf")
                 expect(last_response.body.bytesize).to eq(PDFKit.new("Hello world!").to_pdf.bytesize)
               end
             end
@@ -76,7 +107,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             context "not matching" do
               specify do
                 get 'http://www.example.org/secret/test.pdf'
-                expect(last_response.headers["Content-Type"]).to eq("text/html")
+                expect(last_response.headers["content-type"]).to eq("text/html")
                 expect(last_response.body).to eq("Hello world!")
               end
             end
@@ -88,7 +119,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             context "matching" do
               specify do
                 get 'http://www.example.org/public/test.pdf'
-                expect(last_response.headers["Content-Type"]).to eq("application/pdf")
+                expect(last_response.headers["content-type"]).to eq("application/pdf")
                 expect(last_response.body.bytesize).to eq(PDFKit.new("Hello world!").to_pdf.bytesize)
               end
             end
@@ -96,7 +127,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             context "not matching" do
               specify do
                 get 'http://www.example.org/secret/test.pdf'
-                expect(last_response.headers["Content-Type"]).to eq("text/html")
+                expect(last_response.headers["content-type"]).to eq("text/html")
                 expect(last_response.body).to eq("Hello world!")
               end
             end
@@ -110,7 +141,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             context "matching" do
               specify do
                 get 'http://www.example.org/public/test.pdf'
-                expect(last_response.headers["Content-Type"]).to eq("application/pdf")
+                expect(last_response.headers["content-type"]).to eq("application/pdf")
                 expect(last_response.body.bytesize).to eq(PDFKit.new("Hello world!").to_pdf.bytesize)
               end
             end
@@ -118,7 +149,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             context "not matching" do
               specify do
                 get 'http://www.example.org/secret/test.pdf'
-                expect(last_response.headers["Content-Type"]).to eq("text/html")
+                expect(last_response.headers["content-type"]).to eq("text/html")
                 expect(last_response.body).to eq("Hello world!")
               end
             end
@@ -130,7 +161,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             context "matching" do
               specify do
                 get 'http://www.example.org/public/test.pdf'
-                expect(last_response.headers["Content-Type"]).to eq("application/pdf")
+                expect(last_response.headers["content-type"]).to eq("application/pdf")
                 expect(last_response.body.bytesize).to eq(PDFKit.new("Hello world!").to_pdf.bytesize)
               end
             end
@@ -138,7 +169,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             context "not matching" do
               specify do
                 get 'http://www.example.org/secret/test.pdf'
-                expect(last_response.headers["Content-Type"]).to eq("text/html")
+                expect(last_response.headers["content-type"]).to eq("text/html")
                 expect(last_response.body).to eq("Hello world!")
               end
             end
@@ -156,7 +187,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             context "matching" do
               specify do
                 get 'http://www.example.org/public/test.pdf'
-                expect(last_response.headers["Content-Type"]).to eq("application/pdf")
+                expect(last_response.headers["content-type"]).to eq("application/pdf")
                 expect(last_response.body.bytesize).to eq(PDFKit.new("Hello world!").to_pdf.bytesize)
               end
             end
@@ -164,7 +195,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             context "not matching" do
               specify do
                 get 'http://www.example.org/secret/test.pdf'
-                expect(last_response.headers["Content-Type"]).to eq("text/html")
+                expect(last_response.headers["content-type"]).to eq("text/html")
                 expect(last_response.body).to eq("Hello world!")
               end
             end
@@ -176,7 +207,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             context "matching" do
               specify do
                 get 'http://www.example.org/public/test.pdf'
-                expect(last_response.headers["Content-Type"]).to eq("application/pdf")
+                expect(last_response.headers["content-type"]).to eq("application/pdf")
                 expect(last_response.body.bytesize).to eq(PDFKit.new("Hello world!").to_pdf.bytesize)
               end
             end
@@ -184,7 +215,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             context "not matching" do
               specify do
                 get 'http://www.example.org/secret/test.pdf'
-                expect(last_response.headers["Content-Type"]).to eq("text/html")
+                expect(last_response.headers["content-type"]).to eq("text/html")
                 expect(last_response.body).to eq("Hello world!")
               end
             end
@@ -198,7 +229,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             context "matching" do
               specify do
                 get 'http://www.example.org/public/test.pdf'
-                expect(last_response.headers["Content-Type"]).to eq("application/pdf")
+                expect(last_response.headers["content-type"]).to eq("application/pdf")
                 expect(last_response.body.bytesize).to eq(PDFKit.new("Hello world!").to_pdf.bytesize)
               end
             end
@@ -206,7 +237,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             context "not matching" do
               specify do
                 get 'http://www.example.org/secret/test.pdf'
-                expect(last_response.headers["Content-Type"]).to eq("text/html")
+                expect(last_response.headers["content-type"]).to eq("text/html")
                 expect(last_response.body).to eq("Hello world!")
               end
             end
@@ -218,7 +249,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             context "matching" do
               specify do
                 get 'http://www.example.org/public/test.pdf'
-                expect(last_response.headers["Content-Type"]).to eq("application/pdf")
+                expect(last_response.headers["content-type"]).to eq("application/pdf")
                 expect(last_response.body.bytesize).to eq(PDFKit.new("Hello world!").to_pdf.bytesize)
               end
             end
@@ -226,7 +257,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             context "not matching" do
               specify do
                 get 'http://www.example.org/secret/test.pdf'
-                expect(last_response.headers["Content-Type"]).to eq("text/html")
+                expect(last_response.headers["content-type"]).to eq("text/html")
                 expect(last_response.body).to eq("Hello world!")
               end
             end
@@ -238,8 +269,8 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
       describe "saving generated pdf to disk" do
         before do
           #make sure tests don't find an old test_save.pdf
-          File.delete('spec/test_save.pdf') if File.exists?('spec/test_save.pdf')
-          expect(File.exists?('spec/test_save.pdf')).to eq(false)
+          File.delete('spec/test_save.pdf') if File.exist?('spec/test_save.pdf')
+          expect(File.exist?('spec/test_save.pdf')).to eq(false)
         end
 
         context "when header PDFKit-save-pdf is present" do
@@ -247,7 +278,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
             headers = { 'PDFKit-save-pdf' => 'spec/test_save.pdf' }
             mock_app({}, {only: '/public'}, headers)
             get 'http://www.example.org/public/test_save.pdf'
-            expect(File.exists?('spec/test_save.pdf')).to eq(true)
+            expect(File.exist?('spec/test_save.pdf')).to eq(true)
           end
 
           it "does not raise when target directory does not exist" do
@@ -263,12 +294,157 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
           it "does not saved the .pdf to disk" do
             mock_app({}, {only: '/public'}, {} )
             get 'http://www.example.org/public/test_save.pdf'
-            expect(File.exists?('spec/test_save.pdf')).to eq(false)
+            expect(File.exist?('spec/test_save.pdf')).to eq(false)
+          end
+        end
+      end
+
+      describe 'javascript delay' do
+        context 'when header PDFKit-javascript-delay is present' do
+          it 'passes header value through to PDFKit initialiser' do
+            expect(PDFKit).to receive(:new).with('Hello world!', {
+              root_url: 'http://www.example.com/', protocol: 'http', javascript_delay: 4321
+            }).and_call_original
+
+            headers = { 'PDFKit-javascript-delay' => '4321' }
+            mock_app({}, { only: '/public' }, headers)
+            get 'http://www.example.com/public/test_save.pdf'
+          end
+
+          it 'handles invalid content in header' do
+            expect(PDFKit).to receive(:new).with('Hello world!', {
+              root_url: 'http://www.example.com/', protocol: 'http', javascript_delay: 0
+            }).and_call_original
+
+            headers = { 'PDFKit-javascript-delay' => 'invalid' }
+            mock_app({}, { only: '/public' }, headers)
+            get 'http://www.example.com/public/test_save.pdf'
+          end
+
+          it 'overrides default option' do
+            expect(PDFKit).to receive(:new).with('Hello world!', {
+              root_url: 'http://www.example.com/', protocol: 'http', javascript_delay: 4321
+            }).and_call_original
+
+            headers = { 'PDFKit-javascript-delay' => '4321' }
+            mock_app({ javascript_delay: 1234 }, { only: '/public' }, headers)
+            get 'http://www.example.com/public/test_save.pdf'
+          end
+        end
+
+        context 'when header PDFKit-javascript-delay is not present' do
+          it 'passes through default option' do
+            expect(PDFKit).to receive(:new).with('Hello world!', {
+              root_url: 'http://www.example.com/', protocol: 'http', javascript_delay: 1234
+            }).and_call_original
+
+            mock_app({ javascript_delay: 1234 }, { only: '/public' }, { })
+            get 'http://www.example.com/public/test_save.pdf'
+          end
+        end
+      end
+
+      describe ":disposition" do
+        describe "doesn't overwrite existing value" do
+          let(:headers) do
+            super().merge({
+              'content-disposition' => 'attachment; filename=report-20200101.pdf'
+            })
+          end
+
+          specify do
+            mock_app({}, { :disposition => 'inline' })
+            get 'http://www.example.org/public/test.pdf'
+            expect(last_response.headers["content-disposition"]).to eq('attachment; filename=report-20200101.pdf')
+          end
+        end
+
+        describe "inline or blank" do
+          context "default" do
+            specify do
+              mock_app
+              get 'http://www.example.org/public/test.pdf'
+              expect(last_response.headers["content-disposition"]).to eq("inline")
+            end
+          end
+
+          context "inline" do
+            specify do
+              mock_app({}, { :disposition => 'inline'  })
+              get 'http://www.example.org/public/test.pdf'
+              expect(last_response.headers["content-disposition"]).to eq("inline")
+            end
+          end
+        end
+
+        describe "attachment" do
+          context "attachment" do
+            specify do
+              mock_app({}, { :disposition => 'attachment'  })
+              get 'http://www.example.org/public/test.pdf'
+              expect(last_response.headers["content-disposition"]).to eq("attachment")
+            end
+          end
+
+          context "attachment with filename" do
+            specify do
+              mock_app({}, { :disposition => 'attachment; filename=report.pdf'  })
+              get 'http://www.example.org/public/test.pdf'
+              expect(last_response.headers["content-disposition"]).to eq("attachment; filename=report.pdf")
+            end
+          end
+        end
+      end
+
+      describe "error handling" do
+        let(:error) { StandardError.new("Something went wrong") }
+
+        context "errors raised by PDF generation" do
+          specify do
+            mock_app
+            allow(PDFKit).to receive(:new).and_raise(error)
+            get 'http://www.example.org/public/test.pdf'
+            expect(last_response.status).to eq(500)
+            expect(last_response.body).to eq(error.message)
+          end
+        end
+
+        context "errors raised upstream" do
+          specify do
+            mock_app
+            allow(@app).to receive(:call).and_raise(error)
+
+            expect {
+              get 'http://www.example.org/public/test.pdf'
+            }.to raise_error(error)
           end
         end
       end
     end
 
+    describe "content type header" do
+      before { mock_app }
+
+      context "lower case" do
+        specify "header gets correctly updated" do
+          get 'http://www.example.org/public/test.pdf'
+          expect(last_response.headers["content-type"]).to eq("application/pdf")
+        end
+      end
+
+      context "mixed case" do
+        let(:headers) do
+          {'Content-Type' => "text/html"}
+        end
+
+        specify "header gets correctly updated" do
+          pending("this test only applies to rack 2.x and is rejected by rack 3.x") if Rack.release >= "3.0.0"
+          get 'http://www.example.org/public/test.pdf'
+          expect(last_response.headers["Content-Type"]).to eq("application/pdf")
+        end
+      end
+    end
+
     describe "remove .pdf from PATH_INFO and REQUEST_URI" do
       before { mock_app }
 
@@ -293,7 +469,7 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
           main_app = lambda { |env|
             @env = env
             @env['SCRIPT_NAME'] = '/example.org'
-            headers = {'Content-Type' => "text/html"}
+            headers = {'content-type' => "text/html"}
             [200, headers, @body || ['Hello world!']]
           }
 
@@ -352,22 +528,4 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
       end
     end
   end
-
-  it "does not get stuck rendering each request as pdf" do
-    mock_app
-    # false by default. No requests.
-    expect(@app.send(:rendering_pdf?)).to eq(false)
-
-    # Remain false on a normal request
-    get 'http://www.example.org/public/file'
-    expect(@app.send(:rendering_pdf?)).to eq(false)
-
-    # Return true on a pdf request.
-    get 'http://www.example.org/public/file.pdf'
-    expect(@app.send(:rendering_pdf?)).to eq(true)
-
-    # Restore to false on any non-pdf request.
-    get 'http://www.example.org/public/file'
-    expect(@app.send(:rendering_pdf?)).to eq(false)
-  end
 end
diff --git a/spec/os_spec.rb b/spec/os_spec.rb
index a3ad16ff..d8c5abfa 100644
--- a/spec/os_spec.rb
+++ b/spec/os_spec.rb
@@ -1,4 +1,6 @@
 #encoding: UTF-8
+# frozen_string_literal: true
+
 require 'spec_helper'
 require 'rbconfig'
 
diff --git a/spec/pdfkit_spec.rb b/spec/pdfkit_spec.rb
index 3ff46003..a6c23142 100644
--- a/spec/pdfkit_spec.rb
+++ b/spec/pdfkit_spec.rb
@@ -1,4 +1,6 @@
 #encoding: UTF-8
+# frozen_string_literal: true
+
 require 'spec_helper'
 
 describe PDFKit do
@@ -23,6 +25,13 @@
       expect(pdfkit.source.to_s).to eq(file_path)
     end
 
+    it "accepts a Tempfile as the source" do
+      file_path = File.join(SPEC_ROOT,'fixtures','example.html')
+      pdfkit = PDFKit.new(Tempfile.new(file_path))
+      expect(pdfkit.source).to be_file
+      expect(pdfkit.source.to_s).to match(/^#{Dir.tmpdir}/)
+    end
+
     # Options
     ## options keys
     it "drops options without values" do
@@ -36,8 +45,8 @@
     end
 
     it "transforms complex keys into command-line arguments" do
-      pdfkit = PDFKit.new('html', :replace => {'value' => 'something else'} )
-      expect(pdfkit.options).to have_key('--replace')
+      pdfkit = PDFKit.new('html', :header_left => {'value' => 'something else'} )
+      expect(pdfkit.options).to have_key('--header-left')
     end
 
     it "drops options with false or falsey values" do
@@ -63,8 +72,8 @@
     end
 
     it "parses hash option values into an array" do
-      pdfkit = PDFKit.new('html', :replace => {'value' => 'something else'} )
-      expect(pdfkit.options['--replace']).to eql ['value', 'something else']
+      pdfkit = PDFKit.new('html', :header_left => {'value' => 'something else'} )
+      expect(pdfkit.options['--header-left']).to eql ['value', 'something else']
     end
 
     it "flattens hash options into the key" do
@@ -75,8 +84,8 @@
     end
 
     it "parses array option values into a string" do
-      pdfkit = PDFKit.new('html', :replace => ['value', 'something else'] )
-      expect(pdfkit.options['--replace']).to eql ['value', 'something else']
+      pdfkit = PDFKit.new('html', :header_left => ['value', 'something else'] )
+      expect(pdfkit.options['--header-left']).to eql ['value', 'something else']
     end
 
     it "flattens array options" do
@@ -166,22 +175,36 @@
     it "constructs the correct command" do
       pdfkit = PDFKit.new('html', :page_size => 'Letter', :toc_l1_font_size => 12, :replace => {'foo' => 'bar'})
       command = pdfkit.command
-      expect(command).to include "wkhtmltopdf"
-      expect(command).to include "--page-size Letter"
-      expect(command).to include "--toc-l1-font-size 12"
-      expect(command).to include "--replace foo bar"
+      expect(command.first).to match(/wkhtmltopdf/)
+      expect(command).to contain %w[--page-size Letter]
+      expect(command).to contain %w[--toc-l1-font-size 12]
+      expect(command).to contain %w[--replace foo bar]
+    end
+
+    it "contains a specified by path argument" do
+      pdfkit = PDFKit.new('html')
+      command = pdfkit.command("/foo/bar")
+      expect(command.first).to match(/wkhtmltopdf/)
+      expect(command.last).to eq("/foo/bar")
+    end
+
+    it "contains a specified by path argument of Pathname" do
+      pdfkit = PDFKit.new('html')
+      command = pdfkit.command(Pathname.new("/foo/bar"))
+      expect(command.first).to match(/wkhtmltopdf/)
+      expect(command.last).to eq("/foo/bar")
     end
 
     it "sets up one cookie when hash has only one cookie" do
       pdfkit = PDFKit.new('html', cookie: {cookie_name: :cookie_value})
       command = pdfkit.command
-      expect(command).to include "--cookie cookie_name cookie_value"
+      expect(command).to contain %w[--cookie cookie_name cookie_value]
     end
 
-    it "does not break Windows paths" do
+    it "does not split Windows paths that contain spaces" do
       pdfkit = PDFKit.new('html')
       allow(PDFKit.configuration).to receive(:wkhtmltopdf).and_return 'c:/Program Files/wkhtmltopdf/wkhtmltopdf.exe'
-      expect(pdfkit.command).not_to include('Program\ Files')
+      expect(pdfkit.command).not_to contain(%w[c:/Program Files/wkhtmltopdf/wkhtmltopdf.exe])
     end
 
     it "does not shell escape source URLs" do
@@ -198,15 +221,15 @@
     it "sets up multiple cookies when passed multiple cookies" do
       pdfkit = PDFKit.new('html', :cookie => {:cookie_name1 => :cookie_val1, :cookie_name2 => :cookie_val2})
       command = pdfkit.command
-      expect(command).to include "--cookie cookie_name1 cookie_val1"
-      expect(command).to include "--cookie cookie_name2 cookie_val2"
+      expect(command).to contain %w[--cookie cookie_name1 cookie_val1]
+      expect(command).to contain %w[--cookie cookie_name2 cookie_val2]
     end
 
     it "sets up multiple cookies when passed an array of tuples" do
       pdfkit = PDFKit.new('html', :cookie => [[:cookie_name1, :cookie_val1], [:cookie_name2, :cookie_val2]])
       command = pdfkit.command
-      expect(command).to include "--cookie cookie_name1 cookie_val1"
-      expect(command).to include "--cookie cookie_name2 cookie_val2"
+      expect(command).to contain %w[--cookie cookie_name1 cookie_val1]
+      expect(command).to contain %w[--cookie cookie_name2 cookie_val2]
     end
 
     it "will not include default options it is told to omit" do
@@ -220,42 +243,57 @@
       expect(pdfkit.command).not_to include('--disable-smart-shrinking')
     end
 
-    it "encapsulates string arguments in quotes" do
+    it "must not split string arguments containing spaces" do
       pdfkit = PDFKit.new('html', :header_center => "foo [page]")
-      expect(pdfkit.command).to include "--header-center foo\\ \\[page\\]"
+      expect(pdfkit.command).to contain ['--header-center', 'foo [page]']
     end
 
-    it "sanitizes string arguments" do
+    it "paramatarizes string arguments" do
       pdfkit = PDFKit.new('html', :header_center => "$(ls)")
-      expect(pdfkit.command).to include "--header-center \\$\\(ls\\)"
+      expect(pdfkit.command).to contain %w[--header-center $(ls)]
     end
 
     it "read the source from stdin if it is html" do
       pdfkit = PDFKit.new('html')
-      expect(pdfkit.command).to match /- -$/
+      command = pdfkit.command
+      expect(command[-2]).to eq('-')
+      expect(command[-1]).to eq('-')
     end
 
     it "specifies the URL to the source if it is a url" do
       pdfkit = PDFKit.new('http://google.com')
-      expect(pdfkit.command).to match /"http:\/\/google.com" -$/
+      command = pdfkit.command
+      expect(command[-2]).to eq("http://google.com")
+      expect(command[-1]).to eq("-")
     end
 
     it "does not break Windows paths" do
       pdfkit = PDFKit.new('html')
       allow(PDFKit.configuration).to receive(:wkhtmltopdf).and_return 'c:/Program Files/wkhtmltopdf/wkhtmltopdf.exe'
-      expect(pdfkit.command).not_to include('Program\ Files')
+      expect(pdfkit.command).not_to contain ['Program', 'Files']
     end
 
     it "specifies the path to the source if it is a file" do
       file_path = File.join(SPEC_ROOT,'fixtures','example.html')
       pdfkit = PDFKit.new(File.new(file_path))
-      expect(pdfkit.command).to match /#{file_path} -$/
+      command = pdfkit.command
+      expect(command[-2]).to eq(file_path)
+      expect(command[-1]).to eq('-')
+    end
+
+    it "specifies the path to the source if it is a tempfile" do
+      file_path = File.join(SPEC_ROOT,'fixtures','example.html')
+      pdfkit = PDFKit.new(Tempfile.new(file_path))
+      command = pdfkit.command
+      expect(command[-2]).to start_with(Dir.tmpdir)
+      expect(command[-1]).to eq('-')
     end
 
     it "specifies the path for the ouput if a path is given" do
       file_path = "/path/to/output.pdf"
       pdfkit = PDFKit.new("html")
-      expect(pdfkit.command(file_path)).to match /#{file_path}$/
+      command = pdfkit.command(file_path)
+      expect(command.last).to eq(file_path)
     end
 
     it "detects special pdfkit meta tags" do
@@ -269,8 +307,8 @@
       }
       pdfkit = PDFKit.new(body)
       command = pdfkit.command
-      expect(command).to include "--page-size Legal"
-      expect(command).to include "--orientation Landscape"
+      expect(command).to contain %w[--page-size Legal]
+      expect(command).to contain %w[--orientation Landscape]
     end
 
     it "detects cookies meta tag" do
@@ -284,7 +322,7 @@
       }
       pdfkit = PDFKit.new(body)
       command = pdfkit.command
-      expect(command).to include "--cookie rails_session rails_session_value --cookie cookie_variable cookie_variable_value"
+      expect(command).to contain %w[--cookie rails_session rails_session_value --cookie cookie_variable cookie_variable_value]
     end
 
     it "detects disable_smart_shrinking meta tag" do
@@ -298,7 +336,7 @@
       pdfkit = PDFKit.new(body)
       command = pdfkit.command
       expect(command).to include "--disable-smart-shrinking"
-      expect(command).not_to include "--disable-smart-shrinking true"
+      expect(command).not_to contain %w[--disable-smart-shrinking true]
     end
 
     it "detects names with hyphens instead of underscores" do
@@ -327,8 +365,8 @@
       }
       pdfkit = PDFKit.new(body)
       command = pdfkit.command
-      expect(command).to include "--page-size Legal"
-      expect(command).to include "--orientation Landscape"
+      expect(command).to contain %w[--page-size Legal]
+      expect(command).to contain %w[--orientation Landscape]
     end
 
     it "skips non-pdfkit meta tags" do
@@ -343,8 +381,8 @@
       }
       pdfkit = PDFKit.new(body)
       command = pdfkit.command
-      expect(command).not_to include "--page-size Legal"
-      expect(command).to include "--orientation Landscape"
+      expect(command).not_to contain %w[--page-size Legal]
+      expect(command).to contain %w[--orientation Landscape]
     end
 
     it "does not use quiet when told to" do
@@ -384,19 +422,32 @@
       end
     end
 
+    it "does not use xvfb-run wrapper by default" do
+      pdfkit = PDFKit.new('html')
+      expect(pdfkit.command).not_to include 'xvfb-run'
+    end
+
+    it "uses xvfb-run wrapper when option of using xvfb is configured" do
+      PDFKit.configure do |config|
+        config.use_xvfb = true
+      end
+
+      pdfkit = PDFKit.new('html')
+      expect(pdfkit.command).to include 'xvfb-run'
+
+      PDFKit.configure do |config|
+        config.use_xvfb = false
+      end
+    end
+
     context "on windows" do
       before do
         allow(PDFKit::OS).to receive(:host_is_windows?).and_return(true)
       end
 
-      it "escapes special windows characters" do
-        pdf = PDFKit.new('html', :title => 'hello(world)')
-        expect(pdf.command).to include 'hello^(world^)'
-      end
-
       it "quotes spaces in options" do
         pdf = PDFKit.new('html', :title => 'hello world')
-        expect(pdf.command).to include "--title 'hello world'"
+        expect(pdf.command).to contain ['--title', "hello world"]
       end
     end
   end
@@ -470,6 +521,14 @@
       expect(pdfkit.source.to_s).to include("<style>#{File.read(css)}</style></head>")
     end
 
+    it "can deal with ActiveSupport::SafeBuffer if the HTML doesn't have a head tag" do
+      pdfkit = PDFKit.new(ActiveSupport::SafeBuffer.new "<html><body>Hai!</body></html>")
+      css = File.join(SPEC_ROOT,'fixtures','example.css')
+      pdfkit.stylesheets << css
+      pdfkit.to_pdf
+      expect(pdfkit.source.to_s).to include("<style>#{File.read(css)}</style>")
+    end
+
     it "escapes \\X in stylesheets" do
       pdfkit = PDFKit.new("<html><head></head><body>Hai!</body></html>")
       css = File.join(SPEC_ROOT,'fixtures','example_with_hex_symbol.css')
@@ -481,7 +540,7 @@
     #NOTICE: This test is failed if use wkhtmltopdf-binary (0.9.9.1)
     it "throws an error if it is unable to connect" do
       pdfkit = PDFKit.new("http://google.com/this-should-not-be-found/404.html")
-      expect { pdfkit.to_pdf }.to raise_error /exitstatus=1/
+      expect { pdfkit.to_pdf }.to raise_error PDFKit::ImproperWkhtmltopdfExitStatus, /exitstatus=1/
     end
 
     it "does not throw an error if it is unable to connect", pending: 'this test works for wkhtmltopdf-binary (0.9.9.1)' do
diff --git a/spec/source_spec.rb b/spec/source_spec.rb
index 70f84f9b..b0188197 100644
--- a/spec/source_spec.rb
+++ b/spec/source_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'spec_helper'
 
 describe PDFKit::Source do
@@ -12,6 +14,11 @@
       expect(source).not_to be_url
     end
 
+    it "returns false if passed a tempfile" do
+      source = PDFKit::Source.new(::Tempfile.new(__FILE__))
+      expect(source).not_to be_url
+    end
+
     it "returns false if passed HTML" do
       source = PDFKit::Source.new('<blink>Oh Hai!</blink>')
       expect(source).not_to be_url
@@ -29,6 +36,11 @@
       expect(source).to be_file
     end
 
+    it "returns true if passed a tempfile" do
+      source = PDFKit::Source.new(::Tempfile.new(__FILE__))
+      expect(source).to be_file
+    end
+
     it "returns false if passed a url like string" do
       source = PDFKit::Source.new('http://google.com')
       expect(source).not_to be_file
@@ -51,6 +63,11 @@
       expect(source).not_to be_html
     end
 
+    it "returns false if passed a tempfile" do
+      source = PDFKit::Source.new(::Tempfile.new(__FILE__))
+      expect(source).not_to be_html
+    end
+
     it "returns false if passed a url like string" do
       source = PDFKit::Source.new('http://google.com')
       expect(source).not_to be_html
@@ -58,14 +75,14 @@
   end
 
   describe "#to_input_for_command" do
-    it "URI escapes source URLs and encloses them in quotes to accomodate ampersands" do
-      source = PDFKit::Source.new("https://www.google.com/search?q='cat<dev/zero>/dev/null'")
-      expect(source.to_input_for_command).to eq "\"https://www.google.com/search?q='cat%3Cdev/zero%3E/dev/null'\""
+    it "URI escapes source URI" do
+      source = PDFKit::Source.new("https://www.google.com/search?q=foo bar")
+      expect(source.to_input_for_command).to eq "https://www.google.com/search?q=foo%20bar"
     end
 
     it "does not URI escape previously escaped source URLs" do
-      source = PDFKit::Source.new("https://www.google.com/search?q='cat%3Cdev/zero%3E/dev/null'")
-      expect(source.to_input_for_command).to eq "\"https://www.google.com/search?q='cat%3Cdev/zero%3E/dev/null'\""
+      source = PDFKit::Source.new("https://www.google.com/search?q=foo%20bar")
+      expect(source.to_input_for_command).to eq "https://www.google.com/search?q=foo%20bar"
     end
 
     it "returns a '-' for HTML strings to indicate that we send that content through STDIN" do
@@ -77,6 +94,11 @@
       source = PDFKit::Source.new(::File.new(__FILE__))
       expect(source.to_input_for_command).to match 'spec/source_spec.rb'
     end
+
+    it "returns the file path for tempfile sources" do
+      source = PDFKit::Source.new(file = ::Tempfile.new(__FILE__))
+      expect(source.to_input_for_command).to match file.path
+    end
   end
 
   describe "#to_s" do
@@ -90,6 +112,11 @@
       expect(source.to_s).to eq(__FILE__)
     end
 
+    it "returns a path if passed a tempfile" do
+      source = PDFKit::Source.new(file = ::Tempfile.new(__FILE__))
+      expect(source.to_s).to eq(file.path)
+    end
+
     it "returns the url if passed a url like string" do
       source = PDFKit::Source.new('http://google.com')
       expect(source.to_s).to eq('http://google.com')
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index d2a94bf1..cbd488c9 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 SPEC_ROOT = File.dirname(__FILE__)
 $LOAD_PATH.unshift(SPEC_ROOT)
 $LOAD_PATH.unshift(File.join(SPEC_ROOT, '..', 'lib'))
@@ -6,14 +8,26 @@
   add_filter 'spec/'
 end
 
+Warning[:deprecated] = true if defined?(Warning.[]=)
+
 require 'pdfkit'
 require 'rspec'
 require 'mocha'
 require 'rack'
 require 'rack/test'
 require 'active_support'
-require 'custom_wkhtmltopdf_path' if File.exists?(File.join(SPEC_ROOT, 'custom_wkhtmltopdf_path.rb'))
+require 'custom_wkhtmltopdf_path' if File.exist?(File.join(SPEC_ROOT, 'custom_wkhtmltopdf_path.rb'))
 
 RSpec.configure do |config|
   include Rack::Test::Methods
 end
+
+RSpec::Matchers.define :contain do |expected|
+  match do |actual|
+    (0..(actual.length - expected.length)).any? do |base_index|
+      expected.each_with_index.all? do |expected_element,index|
+        actual[base_index+index] == expected_element
+      end
+    end
+  end
+end