Firefox vertical tabs

Setting it up

0. Install the Sidebery extension.
1. In Sidebery settings:
   1. Set the title preface must as "[S] " (without quotes, trailing space is optional but makes titles more readable). This is used by CSS rules below to identify when Sidebery is active.
   2. Set 'Tabs tree structure' to false -- this stylesheet doesn't adapt to multiple tab levels, but feel free to tweak it!
   3. Copy and paste the SIDEBERY STYLES section in the userChrome.css to Sidebery's Styles Editor → Sidebar.
   4. Optionally sync Sidebery settings to Firefox account to get other customizations.
2. Go to about:support → copy 'user folder' location, setting it as the variable $FF_USER_DIR.
3. Move CSS files to FF user location:
   • mv userChrome.css $FF_USER_DIR/userChrome.css
   • mv userContent.css $FF_USER_DIR/userContent.css
4. Go to about:config → toolkit.legacyUserProfileCustomizations.stylesheets to true.
5. Restart Firefox (about:restartrequired to reopen your current tabs).

Tweaking and Debugging

How to inspect browser interface (source).

1. Enable the Browser Toolbox

   Press F12 to open the Page Inspector. Alternate: Right click the page then "Inspect Element (Q)".

   Press F1 to open the Page Inspector Settings. Alternate: In the top right of the Page Inspector next to the close button; press the "⋯" button then "Settings".

   Ensure the following settings are checked: "Enable Browser chrome and add-on debugging toolbox" "Enable remote debugging"

2. Open the Browser Toolbox

   Press alt, "Tools", "Web Developer" then "Browser Toolbox". Alternate: Press ctrl+alt+shift+i

How to inspect extensions interface

You can use the Browser Toolbox to inspect extensions. Additionally, you can inspect extensions through about:debugging.

1. Navigate to about:debugging.
2. Go to the "This Firefox" page.
3. Find the extension you want to inspect.
4. Press "Inspect" and a console window should open.
5. Change targeted iframe if needed by clicking the blue "layout" icon in the upper right corner, close to the ellipsis menu icon.

Resources

• Firefox release notes
• Firefox source code (GitHub mirror)