Firefox

Firefox 60 for developers

This article provides information about the changes in Firefox 60 that will affect developers. Firefox 60 is the current Beta version of Firefox, and will ship on May 9, 2018.

Stylo comes to Firefox for Android in 60

Firefox's new parallel CSS engine — also known as Quantum CSS or Stylo — which was first enabled by default in Firefox 57 for desktop, has now been enbled in Firefox for Android.

Changes for web developers

Developer tools

  • In the CSS Pane rules view (see Examine and edit CSS), the keyboard shortcuts for precise value increments (increase/decrease by 0.1) have changed from Alt + Up/Down to Ctrl + Up/Down on Linux and Windows, to avoid clashes with default OS-level shortcuts (see bug 1413314).
  • Also in the CSS Pane rules view, CSS variable names will now auto-complete (bug 1422635). If you enter var( into a property value and then type a dash (-), any variables you have declared in your CSS will then appear in an autocomplete list.
  • In Responsive Design Mode, a Reload when... dropdown has been added to allow users to enable/disable automatic page reloads when touch simulation is toggled, or simulated user agent is changed. See Controlling page reload behavior for more details (bug 1428816).
  • The view_source.tab preference has been removed so you can no longer toggle View Source mode between appearing in a new tab or new window. Page sources will always appear in new tabs from now on (bug 1418403).

HTML

Pressing the Enter key in designMode and contenteditable now inserts <div> elements when the caret is in an inline element or text node which is a child of a block level editing host — instead of inserting <br> elements like it used to. If you want to use the old behavior on your app, you can do it with document.execCommand(). See Differences in markup generation for more details (also see bug 1430551).

CSS

SVG

No changes.

JavaScript

APIs

New APIs

DOM

DOM events

No changes.

Service workers

No changes.

Media and WebRTC

Canvas and WebGL

No changes.

CSSOM

No changes.

HTTP

No changes.

Security

The X-Content-Type-Options header, when set to no-sniff, now follows the specification for JavaScript MIME types. In particular, text/json and application/json are no longer valid values (bug 1431095).

Plugins

No changes.

Other

Fetches that include credentials can now share connections with fetches that don't include credentials. For example, if the same origin requests some web fonts as well as some credentialed user data from the same CDN, both could share a connection, potentially leading to a quicker turnaround (bug 1363284).

Removals from the web platform

HTML

No changes.

CSS

JavaScript

The non-standard expression closure syntax has been removed (bug 1426519).

APIs

 

 

SVG

No changes.

Other

No changes.

Changes for add-on and Mozilla developers

WebExtensions

Theme API:

  • headerURL is now optional
  • When creating a browser theme, any text-shadow applied to the header text is removed if no headerURL is specified (see bug 1404688).
  • New properties are supported:
    • tab_line
    • tab_selected
    • popup
    • popup_border
    • popup_text
    • tab_loading
    • icons
    • icons_attention
    • frame_inactive
    • button_background_active
    • button_background_hover

See also

  • Site compatibility for Firefox 60

Older versions

 

Document Tags and Contributors

 Contributors to this page: darby, Sheppy, chrisdavidmills, ntim, evilpie, Masayuki, fscholz
 Last updated by: darby,