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.

Changes for web developers

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 simply writing the regular expression in slashes (bug 1593837).

HTML

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).

attribute of the 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 (bug 1542784). The value of the <style> element's type attribute is now restricted to text/css only, as per the spec (bug 1614329).

CSS

Support for the min() , max() , and clamp() functions has been implemented (bug 1519519).

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

Accessibility

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):

Note: On macOS, we are first waiting for Apple to define what Safari will expose as Apple-dialect attributes to VoiceOver, and will then follow suit.

JavaScript

APIs

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).

interface has a new method, . Unlike the old (and still available) method, acts as if a specified submit button has been clicked, rather than just sending the form data to the recipient. Thus the 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).

event is now represented by an object of type rather than a simple . includes a new property, which is the 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:

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).

HTTP

No changes.

Security

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).

Plugins

No changes.

Security

No changes.

WebDriver conformance (Marionette)

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).

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).

Other

No changes.

Changes for add-on developers

API 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.

(bug 1286953): 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)

Manifest changes

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

See also

Older versions