This article provides information about the changes in Firefox 79 that will affect developers. Firefox 79 was released on July 28, 2020.
See also Firefox 79: The safe return of shared memory, new tooling, and platform updates on Mozilla hacks.
Changes for web developers
- Network messages with response codes in the 400-499 and 500-599 ranges are now considered errors, and are displayed even if Reponse or XHR filters are disabled. (bug 1635460)
- Network messages for requests that are blocked (by the browser or an extension) are now styled with a "prohibited" icon in the Console. (bug 1629875)
- "Blackbox" a source file is now called "ignore" a source file. (bug 1642811)
- Inline preview is now available on exceptions. (bug 1581708)
- Items in the Watch Expressions and Scopes sections now have tooltips on hover, showing their values (bug 1631545)
- In the Call Stack section, there is now a context menu option to Restart Frame, to execute the current stack frame from its beginning. (bug 1594467)
- The new Application panel is now available, which initially provides inspection and debugging support for service workers and web app manifests.
- The Messages tab of the Network Monitor has been merged with the Responses tab. (bug 1636421)
- The Accessibility Inspector is automatically turned on when you access its tab; you no longer need to explicitly enable it. (bug 1602075)
- In Responsive Design Mode, when touch simulation is enabled, mouse-drag events are now interpreted as touch-drag or swipe events. (bug 1621781)
- When remote debugging, the URL bar now has Back and Forward buttons to help with navigation on the remote browser. (bug 1639425)
sandboxattribute now supports the
allow-top-navigation-by-user-activationtoken (bug 1359867).
<area>elements implicitly provides the same behavior as also setting
- External style sheets are now cached per document group (bug 1599160). Firefox will minimize retrieval and revalidation of cached style sheets when navigating pages on the same origin. A simple reload (for example, F5) will not revalidate the cached CSS files. To load current versions of the style sheets, reload the page bypassing the cache (Cmd/Ctrl + F5).
no-preferencevalue has been removed from the media queries spec, and from Firefox (bug 1643656).
SharedArrayBufferhas been re-enabled in a post-Spectre-safe manner. It is available to cross-origin isolated sites (bug 1619649).
Promise.any()is now available (bug 1599769).
WeakRefobjects have been implemented (bug 1639246).
- Logical assignment operators are now supported (bug 1639591)
Atomicsobjects now also work with non-shared memory (bug 1630706).
Intl.DateTimeFormat()constructor now supports the
timeStyleoptions (bug 1557718).
Intl.NumberFormat()constructor now supports more numbering systems (bug 1413504).
- Cross-origin isolation has been implemented using the new
Cross-Origin-Opener-Policy(COOP) headers. This allows you to access certain features such as
SharedArrayBufferobjects and unthrottled timers in
loadstartevent is now dispatched asynchronously, as per the spec (bug 1502403).
CanvasPattern.setTransform()now supports a
DOMMatrixobject as an input parameter, as well as an
SVGMatrixobject (bug 1565997).
Media, WebRTC, and Web Audio
- Firefox now supports remote timestamps on statistics records whose
RTCRemoteOutboundRtpStreamStatsdictionary which is used to provide these statistics now includes the
remoteTimestampproperty, which states the timestamp on the remote peer at which the statistics were collected or generated (bug 1615191).
- A number of internal Gecko events — including
DOMWindowClose— which were accidentally exposed to the web, are now internal-only as intended (bug 1557407).
- WebAssembly Bulk memory operations are now shipped (bug 1528294).
- WebAssembly Reference types are now shipped (bug 1637884).
- WebAssembly Threads (Shared memory & Atomics) are now shipped (bug 1389458, bug 1648685).
Changes for add-on developers
- New API:
- Storage quotas are now enforced for the
syncstorage area (bug 1634615) (addons.mozilla.org blog post)
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