Firefox 115: new ESR base and some add-ons may be blocked from running on certain sites

Mozilla Firefox 115, the latest version of the organization's web browser, is a big update. It moves the browser's Extended Support Release (ESR) base and is the last stable channel version for Windows 7, Windows 8 and 8.1, and also for several macOS versions.

For Firefox ESR users, which are often found in organizations but also at home, Firefox 115 ESR is a massive update. It brings along with it all the changes introduced in Firefox since the release of Firefox 102 ESR. That browser was released a year ago and there have been plenty of changes in Firefox since then.

Windows 7, 8 and 8.1 installations of Firefox will be migrated automatically to Firefox 115 ESR. Mozilla continues to support these operating systems, while all Chromium-based browsers have dropped support by now. Firefox 115 ESR will be supported until September 2024.

Similarly, users of macOS 10.12, 10.13 and 10.14 devices will also be migrated to Firefox 115 ESR to stay supported until September 2024.

Executive Summary

Firefox 115 ESR is the new base of the Extended Support Release channel.

Firefox 115 download and update

Mozilla Firefox 115's and 115 ESR's release date is July 4, 2023. Most browser installations will be updated automatically to the new version.

Firefox users may select Menu > Help > About Firefox to display the current version. Firefox runs a check for updates when the menu is opened and will download the latest version automatically or on the user's request.

Here are the official download locations:

Firefox 115.0 new features and improvements

Some add-ons are blocked from running on certain sites

firefox extensions quarantined

Firefox users who run add-ons that are not monitored by Mozilla may notice a new notification in Firefox when they visit certain sites. The notification informs them that "some extensions are not allowed" and were blocked from running on that site.

Mozilla writes on a support page: "As of Firefox version 115, we have introduced a new back-end feature to only allow some extensions monitored by Mozilla to run on specific websites for various reasons, including security concerns".

Mozilla makes no mention of the scope of this and the support article is extremely vague. The change is called Quarantined Domains by Mozilla.

Firefox users may undo the change in the following way:

Load about:config in the Firefox address bar.
Click Accept the Risk and Continue, if the prompt appears.
Search for extensions.quarantinedDomains.enabled.
Set it to FALSE.
Restart Firefox.

Mozilla should consider publishing detailed information about the blocking in which it reveals all blocking rules.

New Firefox ESR base

Firefox 115 ESR includes all the changes that went into Firefox since the release of Firefox 102 back in 2022.

You may want to consult the following resources to get up to speed regarding the changes:

Firefox 103
- Toolbar access using the keyboard.
Firefox 104
- UI throttling to reduce power usage on devices that run on battery.
- Power usage analysis
Firefox 105
Firefox 106
- Firefox View introduced to improve access to open and closed tabs.
Firefox 107
Firefox 108
- Support for Windows 11's efficiency mode added.
Firefox 109
- Initial support for Manifest V3 extensions.
Firefox 110
- GPU sandboxing support on Windows.
- Option to prevent third-party modules from injecting themselves into Firefox on Windows.
Firefox 111
- Native notifications on Windows support added
Firefox 112
Firefox 113
- Search Terms in the URLbar (instead of the URL)
- Security improvements
- Redesigned accessibility engine
- Picture-in-Picture improvements
Firefox 114
- Secure DNS settings in UI
- Search improvements

Other changes and fixes

Firefox users who migrate from a Chrome-based browser may now import payment methods into Firefox, if they have saved them in the browser they migrate from.
The interface for importing data from other browsers has been streamlined according to Mozilla.
Firefox on Linux systems with Intel GPUs uses hardware video decoding now
Firefox falls back to using Cisco's PpenH264 plugin for playback on systems that do not support H264.
Windows users on "low-end / USB wifi drivers" who have geolocation disabled may now "approve geolocation on a case by case basis without causing system-wide network instability.".
The password fields support undo and redo operations.
A middle-click on the new tab button on Linux will now either load a site, if the clipboard contains an URL, or run a search using the default search provider, if it contains text.
Firefox colorway themes will automatically be migrated to the same theme hosted on Mozilla's add-ons repository.

Developer changes

The CSS animation-composition property is now supported by default.
The Array.fromAsync() static method is now supported.
The Array and TypedArray methods Array.toReversed(), Array.toSorted(), Array.toSpliced(), Array.with(), TypedArrays.toReversed(), TypedArrays.toSorted(), and TypedArrays.with() are now supported.
The Response: json() static method is now supported, making it easier to construct Response objects for returning JSON data.
The Sec-Purpose HTTP fetch metadata request header is now included in requests to Prefetch resources.
The URL.canParse() static method can now be used to parse and validate an absolute URL, or a relative URL and base URL.
The URLSearchParams.has() and URLSearchParams.delete() methods now support the optional value argument.
Support has been added for storage.session, which provides the ability to store data in memory for the duration of the browser session.
IndexedDB is now also supported in private browsing without memory limits thanks to encrypted storage on disk.
The builtin editor now behaves similarly to other browsers with contenteditable and designMode when splitting a node.

Enterprise changes

The FlashPlugin policy is no longer available.
Firefox 102 ESR continues to be supported for another two releases before Firefox 115 ESR becomes the sole Extended Support Release.