Firefox 85 for developers

This article provides information about the changes in Firefox 85 that will affect developers. Firefox 85 was released on January 26, 2021.

Note: See also January brings us Firefox 85 on Mozilla Hacks.

Changes for web developers

Developer Tools





  • The collation property can now be specified in the options passed to the Intl.Collator() constructor (Firefox bug 1670062). This allows developers to write code with greater clarity:
    // Old method
    let pinyin = new Intl.Collator(["zh-u-co-pinyin"]);
    // New method
    let pinyin = new Intl.Collator("zh", { collation: "pinyin" });



No changes.

WebDriver conformance (Marionette)

  • Fixed a potential page load timeout situation when WebDriver:ElementClick is called for a link with a target other than _blank (Firefox bug 1678455).
  • Using web element references on browsing contexts other than the originating one now correctly returns a no such element error instead of a stale element reference error (Firefox bug 1684827).

Known bugs

  • WebDriver commands following a call to WebDriver:SwitchToFrame can fail with a "no such window" error if the frame's content hasn't yet finished loading (Firefox bug 1691348).
  • After a cross-group page navigation, accessing a previously-retrieved element might not always raise a "stale element" error, and can also lead to a "no such element" error. To prevent this, set the marionette.actors.enabled preference to false (Firefox bug 1690308).

Changes for add-on developers

No changes.

Older versions