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Mozilla today launched Firefox 73 for Windows, Mac, Linux, and Android. Firefox 73 includes a default zoom level setting, a readability backplate option, and a handful of developer features. There isn’t too much else here — Mozilla has now transitioned Firefox releases to a four-week cadence (from six to eight weeks).

You can download Firefox 73 for desktop now from, and all existing users should be able to upgrade to it automatically. The Android version is trickling out slowly on Google Play. According to Mozilla, Firefox has about 250 million active users, making it a major platform for web developers to consider.

Default zoom level and readability backplate

Firefox lets you set the zoom level on a per-site basis, which can be quite painful if you’re a user who wants to zoom most websites. Firefox 73 thus implements a new global default zoom level setting (about:preferences => Language and Appearance). You can set the default zoom level for all sites by scaling the magnification up or down from 100% as needed. You can also specify whether to enlarge only text or all page contents. Various Firefox extensions have offered this functionality for readability purposes, but it’s now a native feature.

Speaking of readability, Mozilla has changed how it handles Windows’ High Contrast Mode. Until now, Firefox disabled background images when High Contrast Mode was enabled. Firefox 73 introduces a “readability backplate” option that places a block of background color between the text and background image. As a result, High Contrast Mode can increase the readability of a website’s text without disabling background images.

You’ll notice that both of these features are accessibility improvements that anyone can use. They are aimed at helping users view and read website content more easily, something all browser users can take advantage of.

Windows, Mac, and Linux

There are a few other small additions in this release, especially for developers. The WebSocket inspector that shipped late last year in Firefox 71 now prints WAMP-formatted messages. The console is now smarter, thanks to various script authoring and logging improvements. Lastly, Firefox has gained a few web platform additions, including CSS logical properties overscroll-behavior-block and overscroll-behavior-inline, yearName and relatedYear fields in DateTimeFormat.prototype.formatToParts(), and requestSubmit() in the HTMLFormElement interface.

Here’s the full Firefox 73 for desktop changelog:

  • Firefox has offered a page zoom feature for more than a decade that allows users to set the zoom level on a per-site basis. For users who need to zoom most websites, having to adjust zoom for each new site can be an annoyance. To address this, we have implemented a new global default zoom level setting. This option is available in about:preferences under “Language and Appearance” and can be scaled up or down from 100% as needed and sets the default zoom level for all sites. Per-site zoom is still available to make adjustments to individual sites as needed.
  • Many users with low vision rely on Windows’ High Contrast Mode to make websites more readable. Traditionally, to increase the readability of text, Firefox has disabled background images when High Contrast Mode is enabled. With today’s release of Firefox 73, we introduce a “readability backplate” solution which places a block of background color between the text and background image. Now, websites in High Contrast Mode are more readable without disabling background images.
  • Sync now supports the Multi-Account Containers extension so you can share containers and their associated sites across desktop devices with a Firefox Account.
  • WAMP-formatted WebSocket messages (JSON, MsgPack, and CBOR) are now nicely decoded for inspection in the Network panel.
  • Various security fixes.
  • Improved audio quality when playing back audio at a faster or slower speed.
  • Firefox will now only prompt you to save logins if a field in a login form was modified.
  • WebRender will roll out to laptops with Nvidia graphics cards with drivers newer than 432.00 and screen sizes smaller than 1920×1200.
  • Improved auto-detection of legacy text encodings on old web pages which don’t explicitly declare the text encoding.

If you’re a web developer, you’ll want to get more details here: Firefox 73 for developers.


Firefox for Android is still barely getting updates. The latest changelog is just two bullet points:

  • Updated messaging card on the home screen to inform users about upcoming releases.
  • Security and stability fixes.

The lack of notable additions is due to the Android team working on Firefox Preview, a new version of Firefox for Android powered by GeckoView. Mozilla plans to launch the new Firefox for Android in the first half of 2020.

As mentioned, Mozilla is now on a four-week Firefox release cycle. Firefox 74 is currently slated for March.


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