Firefox 153 contains itself while Thunderbird 153 fixes almost everything

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Firefox 153 contains itself while Thunderbird 153 fixes almost everything

Mozilla walls off your online identities as MZLA unleashes a bumper repair job

Liam Proven

Liam<br>Proven

LINUX AND OPEN SOURCE REPORTER

Published<br>thu 23 Jul 2026 // 12:14 UTC

Mozilla released Firefox 153 on Tuesday, closely followed by MZLA with Thunderbird 153 – codenamed "Meadow" for reasons that remain obscure for now.<br>Firefox 153 is Mozilla's new Extended Support Release (ESR), so it will receive security updates until some time after the next ESR in mid-2027. We covered the highlights of what's new in this version last week.<br>Firefox 153 will be good news if you used the Multi-Account Containers extension: a preview version of the functionality is now built in. Firefox already has user profiles, which let you keep sets of settings and credentials separate. With some extra effort, you can even launch multiple separate instances of Firefox with different profiles. Containers make similar functionality much easier: each container has its own set of stored credentials. So, for instance, a "home" container could hold a set of tabs logged into various sites with your personal accounts, while a "work" container could log into the same sites with your day-job credentials.

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There are also new features for users on mobile. Firefox 153 for Android gets tab groups, while Firefox for iOS users in the US get the new Quick Answers feature. Speech recognition happens on the device, although the transcribed question is sent online to generate an answer.

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Thunderbird 'Meadow'<br>MZLA's Thunderbird messaging client also has a new version, itself an ESR: Thunderbird 153.<br>This version is codenamed "Meadow," replacing the previous "Eclipse" release, but at the time of writing, info about what "Meadow" signifies is scant. The New in Thunderbird Desktop page hasn't been updated since Thunderbird 150, which came out back in April. At least there's some info there, even if it's outdated. At the time of writing, following the What's New in Thunderbird 153 link in the release notes gives this helpful info:

Thunderbird 153 is here, with hundreds of fixes and tweaks – not that MZLA wants to tell us about it<br>Liam Proven

Since that final link is the only helpful thing there, we've done so. It might even be fixed by the time you read this.

Firefox 115.38

Some ESRs get updates for much longer. Although Firefox 115 came out three years ago, the same day as Firefox on our Sequoia iMac updated itself to version 153, The Reg FOSS desk's last remaining macOS 10.13 machine got Firefox 115.38. Good news for the determined users of Windows 7 to 8.1, and macOS 10.12 to 10.14.

Perhaps the team has been too busy fixing things instead, which seems like respectable prioritization to us. Under What's New are 32 refinements, 15 entries under What's Changed, and a whopping 181 bug fixes under What's Fixed.<br>This many changes is good news for an ESR release, and it looks like the team has been busy fixing things. It does make us wonder if MZLA is struggling to keep up with Firefox's monthly release schedule, as it's been doing since Thunderbird 138 in April 2025. Since Mozilla decided to accelerate Firefox to fortnightly releases from September, perhaps MZLA should drop Thunderbird back down to annual releases.

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Firefox 152 understands 'Sssh!'

Still, this ESR brings improvements to folder handling, notifications, OpenPGP encryption, OAuth login, address book export, PDF handling, and much more. There won't be any more 32-bit Linux binaries – joining Firefox, which did that in September after Firefox 144. "Junk" mail is now called "Spam," and the dedicated setup option for the Russian Odnoklassniki service has been dropped, with users directed to configure it through XMPP instead.<br>Thunderbird offers so many different views that we've seen some user confusion about this, but they are handy, and a few of the non-default ones are improved in this release. We sometimes use the "Unread Folders" view, and it's now better at hiding folders with no unread messages. The other non-obvious view is "Unified Folders." This categorizes and combines multiple inboxes into one tree: all your inboxes, followed by separate per-account trees of all subfolders. It sounds confusing, but we find it very helpful. This view now lets you color-code different accounts.

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Several of Thunderbird's new options around account handling concern Thundermail accounts. These are part of MZLA's paid email service, Thunderbird Pro. This hasn't been launched yet, but the new account type suggests it's getting close. One of the...