Mozilla has released a new stable version of Firefox a moment ago. Firefox 133 is the latest version of the open source browser.

It includes several major improvements, including protection against bounce tracking, and also security fixes.

The two maintained Firefox Extended Support Release versions, Firefox 115 and 128, are also updated today.

The details:

• Bounce Tracking protection protects Firefox users against another common type of tracking.
• Windows users benefit from GPU-accelerated Canvas2D, which improves performance and is now enabled by default.
• Security fixes.

Firefox 133.0 download and update

Firefox 133 is available already. Most Firefox installations should receive the update automatically in the coming days.

If you do not want to wait, you may either check for updates in Firefox or download the latest version directly from Mozilla.

Do the following to check for updates in Firefox:

1. Select Menu > Help > About Firefox.

Firefox checks for updates when the help prompt opens. It should find the update and install it at this point.

Firefox 133 is also available as a direct download from Mozilla's official site. None-stable downloads are also available.

• Firefox Beta download
• Nightly download
• Firefox ESR download

Firefox 133: the major changes

Bounce Tracking Protection

Some advertisers and data brokers use redirects for tracking. This process is invisible to the user, as it happens very fast.

The core idea is simple: a click on a link opens a tracking server first before the destination is opened.

Bounce Tracking protection attempts to block this by purging cookies and site data regularly.

Note: the feature is only enabled for users who have set the Enhanced Tracking Protection feature to strict in Firefox. This is not the default value of the setting.

Brave Browser supported this form of protection for several years already. Unlike Mozilla's solution, which appears to react to bounce trackers only by deleting cookies and site data, Brave's solution attacks bounce tracking in several ways.

The browser uses a list of known bounce trackers, which are blocked. It also warns users of suspected bounce tracking, but only if "aggressively block trackers & ads" is enabled. The browser uses temporary storage, which Brave calls Unlinkable Bouncing, to make tracking less effective.

Other changes and fixes

• The Tab overview menu includes a new item to view tabs from other devices.
• Windows users benefit from GPU-accelerated Canvas2D. It should improve performance in Firefox for Windows.
• Picture-in-Picture mode's auto-open feature should work more reliably now. It is disabled by default and needs to be enabled in Firefox Labs.

Developer changes

Check the Developers link at the bottom of the page for all changes for developers.

• Support for Uint8Array methods to ease conversions between base64- and hex-encoded strings and byte arrays.
• The WorkerNavigator.permissions property is now supported.
• The EventSource interface to handle server-sent events is now supported in service workers.
• The ImageDecoder, ImageTrackList, and ImageTrack interfaces of the WebCodecs API are now supported.

Enterprise changes

• Firefox supports the MicrosoftEntraSSO policy fully in Firefox 133 and ESR 128.5.
• Preference policy supports security.pki.certificate_transparency.mode now.
• Preferences policy now supports preferences that begin with identity.fxaccounts.toolbar.

Security updates / fixes

The aggregate severity rating is high. Mozilla patched a total of 17 unique security issues or potential security issues in Firefox 133. No exploits in the wild mentioned by Mozilla.

Outlook

Firefox 133 was the last major release this year. Mozilla plans to release Firefox 134 on January 7, 2025. The same applies to Firefox 115.19 and 128.6, both ESR, which will also be released on the day.

Additional information / resources

• Firefox 133 release notes
• Firefox 133 for Developers
• Firefox 133 for Enterprise
• Firefox Security Advisories
• Firefox Release Schedule

Closing Words

Bounce Tracking protection is a good new feature. Mozilla is a bit late to the party, but better late than never. The feature is only enabled for users who enable strict protection, which limits its availability.

It is possible that Mozilla is going to collect data and feedback before it makes a decision to push this further.

Do you use Firefox? Did you upgrade your version to version 133 or one of the supported ESR versions? Anything that you like or do not like? Feel free to leave a comment down below.