diff --git a/action.yml b/action.yml
index 8ac668b..bcd3daf 100644
--- a/action.yml
+++ b/action.yml
@@ -144,6 +144,10 @@ runs:
       run: echo "${{ inputs.config }}" >> hyde.yml
       shell: bash
 
+    - name: Check site URL configuration
+      run: bash check-site-url.sh
+      shell: bash
+
     # TODO: Add pre-build hook to run some bash commands?
 
     - name: Build the site
diff --git a/docs/index.md b/docs/index.md
index a15cd84..96b8be7 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -254,3 +254,11 @@ Sets the `SITE_URL` environment variable
 > Deprecated: Use the `env` input instead with `TORCHLIGHT_TOKEN=value`
 
 Sets the `TORCHLIGHT_TOKEN` environment variable
+
+### Site URLs
+
+It's highly recommended to set the site URL for your project so that sitemaps and meta tags are generated correctly.
+
+You can do this by setting the `SITE_URL` environment variable, or by adding the `url` key to your `hyde.yml` file or `config/hyde.php` file.
+
+If the site URL is not set, the action will output a warning and suggest a solution. An easy way to set the site URL is to use the `env` input as seen above.
diff --git a/src/check-site-url.sh b/src/check-site-url.sh
new file mode 100755
index 0000000..a9c3a3d
--- /dev/null
+++ b/src/check-site-url.sh
@@ -0,0 +1,37 @@
+#!/bin/bash
+
+# Function to check if SITE_URL is effectively set
+check_site_url() {
+    # Check if SITE_URL is set in .env file
+    if grep -q "^SITE_URL=" .env; then
+        return 0
+    fi
+
+    # Check for hyde.yml or hyde.yaml with any url setting
+    if [ -f "hyde.yml" ] && grep -q "^[[:space:]]*url:" hyde.yml; then
+        return 0
+    fi
+    
+    if [ -f "hyde.yaml" ] && grep -q "^[[:space:]]*url:" hyde.yaml; then
+        return 0
+    fi
+
+    # If config/hyde.php exists, check if it has a non-localhost URL
+    if [ -f "config/hyde.php" ]; then
+        # Look for url configuration line and exclude localhost
+        if grep -q "'url' => env('SITE_URL'," config/hyde.php; then
+            line_number=$(grep -n "'url' => env('SITE_URL'," config/hyde.php | cut -d: -f1)
+            if ! grep -q "'url' => env('SITE_URL', 'http://localhost')," config/hyde.php; then
+                return 0
+            fi
+            echo "::warning file=config/hyde.php,line=$line_number,title=Missing Site URL::The site URL is set to localhost in your configuration file. Consider setting a production URL here or in using the 'env' input with 'SITE_URL=https://example.com'"
+            return 0
+        fi
+    fi
+
+    echo "::warning title=Missing Site URL::No SITE_URL environment variable found. It's recommended to set a production URL for your site. You can set it using the 'env' input with 'SITE_URL=https://example.com'"
+    return 0
+}
+
+# Show warning if SITE_URL is not properly set
+check_site_url
diff --git a/tests/unit/test-check-site-url.sh b/tests/unit/test-check-site-url.sh
new file mode 100755
index 0000000..85ecc4e
--- /dev/null
+++ b/tests/unit/test-check-site-url.sh
@@ -0,0 +1,97 @@
+#!/bin/bash
+
+test_site_url_warnings() {
+    base_dir="$(pwd)"
+    temp_dir=$(mktemp -d)
+    cd "$temp_dir"
+
+    # Test case 1: No SITE_URL set anywhere
+    touch .env
+    output=$(bash "$base_dir/src/check-site-url.sh")
+    expected="::warning title=Missing Site URL::No SITE_URL environment variable found. It's recommended to set a production URL for your site. You can set it using the 'env' input with 'SITE_URL=https://example.com'"
+    
+    if [[ "$output" != "$expected" ]]; then
+        echo "Test 1 failed: Warning not shown when SITE_URL is missing"
+        echo "Expected: $expected"
+        echo "Got: $output"
+        cd "$base_dir"
+        rm -rf "$temp_dir"
+        exit 1
+    fi
+
+    # Test case 2: SITE_URL is set in .env
+    echo "SITE_URL=https://example.com" > .env
+    output=$(bash "$base_dir/src/check-site-url.sh")
+    
+    if [[ -n "$output" ]]; then
+        echo "Test 2 failed: Warning shown when SITE_URL is set"
+        echo "Expected empty output"
+        echo "Got: $output"
+        cd "$base_dir"
+        rm -rf "$temp_dir"
+        exit 1
+    fi
+
+    # Test case 3: SITE_URL set in config with non-localhost value
+    rm .env
+    mkdir -p config
+    echo "'url' => env('SITE_URL', 'https://example.com')," > config/hyde.php
+    output=$(bash "$base_dir/src/check-site-url.sh")
+    
+    if [[ -n "$output" ]]; then
+        echo "Test 3 failed: Warning shown when SITE_URL is set in config"
+        echo "Expected empty output"
+        echo "Got: $output"
+        cd "$base_dir"
+        rm -rf "$temp_dir"
+        exit 1
+    fi
+
+    # Test case 4: SITE_URL in config but with localhost
+    echo "'url' => env('SITE_URL', 'http://localhost')," > config/hyde.php
+    output=$(bash "$base_dir/src/check-site-url.sh")
+    expected="::warning file=config/hyde.php,line=1,title=Missing Site URL::The site URL is set to localhost in your configuration file. Consider setting a production URL here or in using the 'env' input with 'SITE_URL=https://example.com'"
+    
+    if [[ "$output" != "$expected" ]]; then
+        echo "Test 4 failed: Warning not shown when SITE_URL is localhost"
+        echo "Expected: $expected"
+        echo "Got: $output"
+        cd "$base_dir"
+        rm -rf "$temp_dir"
+        exit 1
+    fi
+
+    # Test case 5: URL set in hyde.yml
+    rm config/hyde.php
+    echo "url: http://localhost" > hyde.yml
+    output=$(bash "$base_dir/src/check-site-url.sh")
+    
+    if [[ -n "$output" ]]; then
+        echo "Test 5 failed: Warning shown when URL is set in hyde.yml"
+        echo "Expected empty output"
+        echo "Got: $output"
+        cd "$base_dir"
+        rm -rf "$temp_dir"
+        exit 1
+    fi
+
+    # Test case 6: URL set in hyde.yaml with indentation
+    rm hyde.yml
+    echo "    url: example.com" > hyde.yaml
+    output=$(bash "$base_dir/src/check-site-url.sh")
+    
+    if [[ -n "$output" ]]; then
+        echo "Test 6 failed: Warning shown when URL is set in hyde.yaml"
+        echo "Expected empty output"
+        echo "Got: $output"
+        cd "$base_dir"
+        rm -rf "$temp_dir"
+        exit 1
+    fi
+
+    cd "$base_dir"
+    rm -rf "$temp_dir"
+}
+
+# Run the tests
+test_site_url_warnings