Firefox 68 for developers

This article provides information about the changes in Firefox 68 that will affect developers. Firefox 68 was released on July 9, 2019.

Changes for web developers

Developer tools

Browser/web console

JavaScript debugger

  • You can now Search in all files in the current project from the debugger by pressing Shift + Ctrl + F (Windows or Linux) or Shift + Cmd + F (macOS) (Firefox bug 1320325).

Network monitor

  • The Network monitor request list now allows you to block a specific URL (Firefox bug 1151368).
  • You can now resend a network request without editing the method, URL, parameters, and headers, using the Resend command on the context menu (Firefox bug 1422014).
  • The context menu of the Network monitor Headers tab now allows you to copy all or some of the header information to the clipboard in JSON format (Firefox bug 1442249).

Page inspector

  • A button has been added to the rules panel of the Page inspector that allows you to toggle the display of any print media queries (Firefox bug 1534984).
  • The fonts panel now includes a slider to modify letter-spacing (Firefox bug 1536237).
  • A warning icon appears next to unsupported CSS properties or rules that have invalid values, to help you understand why certain styles are not being applied (Firefox bug 1306054).

Storage inspector


  • The Accessibility Inspector now includes a new Check for issues feature, which will include a number of audit tools to highlight accessibility problems on your web pages. The first available check is contrast, for highlighting color contrast problems.
  • The preference that controls the visibility of internal extensions (system add-ons and hidden extensions) on the about:debugging page has been changed from devtools.aboutdebugging.showSystemAddons to devtools.aboutdebugging.showHiddenAddons (Firefox bug 1544372).
  • Responsive design mode has been redesigned — the Device Settings dialog (device selection menu > Edit List…) is now more intuitive and simpler to use (Firefox bug 1487857).



  • The <track> element — represented by HTMLTrackElement — now receives a cuechange event in addition to the TextTrack itself, if the text track is a contained by a media element (Firefox bug 1548731).
  • <link> elements support the disabled attribute again, albeit with different behavior. When disabled is set on a <link> element along with rel="stylesheet", the referenced stylesheet is not loaded during page load, and will be loaded on demand when the disabled attribute is changed to false or removed (Firefox bug 1281135).




  • scroll-snap-coordinate, scroll-snap-destination, scroll-snap-type-x and scroll-snap-type-y have been removed.
  • The scroll-snap-type property has become a longhand, so the old shorthand syntax like scroll-snap-type:mandatory will stop working.


No changes.



CSS Object Model (CSSOM)

  • The legacy rules property and addRule() and removeRule() methods have been added to the CSSStyleSheet interface. These were introduced by Internet Explorer 9 and have never managed to quite be stamped out, so they have been added to improve compatibility with the small percentage of sites that still use them (Firefox bug 1545823).


DOM events

  • Firefox for Android no longer incorrectly sends a resize event until after the first frame is painted; this improves web compatibility with sites that don't expect this event to occur (Firefox bug 1528052).
  • The dispatching of events for non-primary mouse buttons has been made to more closely follow the specification; the click event is no longer sent when non-primary buttons are clicked, instead using auxclick. In addition, dblclick no longer fires for non-primary buttons (Firefox bug 1379466).
  • The proprietary mozPressure property has been deprecated, and will now trigger a warning in the console (Firefox bug 1165211).

Media, Web Audio, and WebRTC



  • The HTTP Clear-Site-Data header no longer supports the executionContexts directive. This was removed due to problems with interactions between interconnections among different kinds of data at different points in the navigation process and the way the specification is designed. It has been proposed that this directive be removed from the specification for this reason, among others (Firefox bug 1548034).


  • The Content-Security-Policy directive require-sri-for is no longer supported due to concerns about its standardization status. It was previously available only behind a preference, which was off by default (Firefox bug 1386214).


WebDriver conformance (Marionette)

Bug fixes

  • If WebDriver:SwitchToWindow changes the selection to a different window it now waits for its focus and activate events before returning (Firefox bug 1335085).
  • Fixed the TypeError: this.tabModal is null failure, which sometimes appeared when interacting with modal dialogs or user prompts (Firefox bug 1538782)


  • Disabled the feature to force unloading background tabs on low memory conditions, to prevent top-level browser contexts from magically disappearing (Firefox bug 1553748).
  • Disabled privileged content processes that caused HTTP authentication dialogs not to appear when navigating to a website after opening a new tab (Firefox bug 1558763).


No changes.

Changes for add-on developers

API changes

Manifest changes

No changes.

See also

Older versions