Firefox 75 for developers

This article provides information about the changes in Firefox 75 that will affect developers. Firefox 75 was released on April 7, 2020.

See also the accompanying hacks post — Firefox 75: Ambitions for April.

• It is now possible to resize the rectangle of the Measuring Tool (bug 1152321).
• In the inspector, you can now use XPath expressions to locate elements, in addition to locating elements using CSS selectors as before (bug 963933).
• You can now filter WebSocket messages using regular expressions, in addition to plain text search, by writing the regular expression in slashes (bug 1593837).

• The loading attribute of the <img> element has now been implemented. This string value can be used to specify that the image should be lazily loaded, by setting its value to lazy (bug 1542784).
• The value of the <style> element's type attribute is now restricted to text/css only, as per the spec (bug 1614329).

• Support for the min(), max(), and clamp() functions has been implemented (bug 1519519).
• The all value of the text-decoration-skip-ink property has been added (bug 1611965)

The new roles and objects related to ARIA annotations are now exposed in Firefox, on Windows and Linux (bear in mind that these still won't be usable until screenreaders start to support them):

• aria-description (bug 1608961).
• role="mark" and role="suggestion" (bug 1608965).
• role="comment" (bug 1608969).
• Multiple IDs on aria-details (bug 1608883).

• Public static class fields are now supported (bug 1535804).
• The Intl.Locale class is now supported (bug 1613713).
• The Function.caller property has been updated to be aligned with the latest ECMAScript spec proposal. Previously throwing a TypeError, it now returns null if the caller is a strict, async, or generator function (bug 1610206).

DOM

• The HTMLFormElement interface has a new method, requestSubmit(). Unlike the old (and still available) submit() method, requestSubmit() acts as if a specified submit button has been clicked, rather than just sending the form data to the recipient. Thus the submit event is delivered and the form is checked for validity prior to the data being submitted (bug 1613360).
• The submit event is now represented by an object of type SubmitEvent rather than a simple Event. SubmitEvent includes a new submitter property, which is the Element that was invoked to trigger the form submission. With this event, you can have a single handler for submit events that can discern which of multiple submit buttons or links was used to submit the form (bug 1588715).
• Calling the click() method on a detached element (one not part of a DOM tree) now functions normally, leading to a click event being sent to it (bug 1610821).

Web animations API

Firefox 75 sees numerous additions to the Web Animations API:

• Implicit to/from keyframes are now supported, as is automatically removing filling animations that have been replaced by other indefinitely filling animations (bug 1618773). This includes enabling of support for:
  • Animation.commitStyles()
  • Animation.onremove
  • Animation.persist()
  • Animation.replaceState
• The Animation.timeline getter, Document.timeline, DocumentTimeline, and AnimationTimeline features are now enabled by default (bug 1619178).
• The Document.getAnimations() and Element.getAnimations() methods are now enabled by default (bug 1619821).

Media, Web Audio, and WebRTC

• The RTCPeerConnection.setLocalDescription() method can now be called without arguments, in which case the WebRTC runtime will try to create the new local session description itself (bug 1568292).

No changes.

• CSP nonces from non-script sources, such as CSS selectors, and .getAttribute("nonce") calls, are now hidden. Instead, check the .nonce property to access nonces from scripts (bug 1374612).

No changes.

No changes.

• Fixed a bug that always caused Marionette to initialize when Firefox starts-up. It has been limited to the command line argument and environment variable now (bug 1622012).
• Fixed WebDriver:Print to no longer add extra margins to the document (bug 1616932).
• Changed the preference value for network.http.speculative-parallel-limit to 0, to no longer force-disable speculative connections (bug 1617869).

No changes.

• We've added some new settings in browserSettings (bug 1286953):
  • browserSettings.zoomSiteSpecific to control whether zooming is on a per-site or per-tab basis
  • browserSettings.zoomFullPage to control whether zoom is applied to the entire page or to text only.
• The name of the file used when saving a PDF with tabs.saveAsPDF can be specified using toFileName in the type tabs.PageSettings.(bug 1483590)

• The "privacy" permission is now optional. (bug 1618399)