Firefox 62 for developers

This article provides information about the changes in Firefox 62 that will affect developers. Firefox 62 was released on September 5, 2018.

Changes for web developers

Developer tools

  • The Shape Path Editor is now available by default — see Edit Shape Paths in CSS for more information.
  • You can now split the Rules view out into its own pane, separate from the other tabs on the CSS pane. See Page inspector 3-pane mode for more details.
  • The Grid inspector has updated features, and all new documentation — see CSS Grid Inspector: Examine grid layouts.
  • You now have four options for the location of the Developer Tools. In addition to the default location on the bottom of the window, you can choose to locate the tools on either the left or right sides of the main window or in a separate window (bug 1192642).
  • A close button has been added to the split console toolbar.
  • If the option to "Select an iframe as the currently targeted document" is checked, the icon will appear in the toolbar while the Settings tab is displayed, even if the current page doesn't include any iframes (bug 1456069).
  • The Network Monitor's Cookies tab now shows the cookie samesite attribute (bug 1452715).
  • Responsive design mode now works inside container tabs (bug 1306975).
  • When CORS errors occur and are reported on the console, Firefox now provides a link to the corresponding page in our CORS error documentation (bug 1475391).
  • Create a screenshot of the current page (with an optional filename) from the Console tab (bug 1464461) using the following command:

    :screenshot <filename.png> --fullpage

    where <filename.png> is the desired filename. The file will be saved to your downloads folder. The --fullpage parameter is optional, but if included, it will save the full web page. This option also adds -fullpage to the name of the file. For a list of all options available for this command, enter: :screenshot --help


  • The Developer Toolbar/GCLI (accessed with Shift + F2), has been removed from Firefox (bug 1461970). Both the Developer Toolbar UI and the GCLI upstream library have become unmaintained, some of its features are broken (some ever since e10s), it is blocking the unsafeSetInnerHTML work, usage numbers are very low, alternatives exist for the most used commands.


No changes.




No changes.



  • The DOMPoint and DOMPointReadOnly constructors no longer support an input parameter of type DOMPointInit; the values of the properties must be specified using the x, y, z, and w parameters (bug 1186265).
  • The URL.createObjectURL() method no longer supports creating object URLs to represent a MediaStream. This capability has been obsolete for some time, since you can now set HTMLMediaElement.srcObject to the MediaStream directly (bug 1454889).


New APIs


DOM events

No changes.

Service workers

No changes.

Media, Web Audio, and WebRTC

  • The "media.autoplay.enabled" preference now controls automatic playback of both audio and video media, instead of just video media (bug 1413098).
  • The ChannelSplitterNode has been fixed to correctly default to having 6 channels with the channelInterpretation set to "discrete" and the channelCountMode set to "explicit", as per the specification (bug 1456265).





No changes.


No changes.

WebDriver conformance (Marionette)

New features

  • Command WebDriver:ElementSendKeys has been made WebDriver conforming for file uploads (bug 1448792).

  • User prompts as raised by beforeunload events are automatically dismissed for WebDriver:Get, WebDriver:Back, WebDriver:Forward, WebDriver:Refresh, and WebDriver:Close commands (bug 1434872).

  • WebDriver:PerformActions for Ctrl + Click synthesizes a contextmenu event (bug 1421323).

API changes

  • Removed obsolete endpoints including getWindowPosition, setWindowPosition, getWindowSize, and setWindowSize (bug 1348145).
  • WebDriver commands which return success with data null now return an empty dictionary (bug 1461463).

Bug fixes

  • WebDriver:ExecuteScript caused cyclic reference error for WebElement collections (bug 1447977).

  • Dispatching a pointerMove or pause action primitive could cause a hang, and the command to never send a reply (bug 1467743, bug 1447449).


No changes.

Changes for add-on developers

API changes

Manifest changes

Theme changes

  • New tab_background_separator property of the theme manifest key enables extensions to change the color of the tab separator (bug 1459455).


  • Support for unpacked sideloaded extensions has been removed (bug 1385057).
  • The warning about browser_style displayed when temporarily loading an extension for testing is no longer displayed (bug 1404724).

Older versions