Firefox to Ship Major Releases Every Two Weeks Starting in September

Two weeks instead of four. Starting September 1, 2026, Mozilla plans to release a new major version of Firefox every fifteen days on Desktop and Android. The shift will begin with Firefox 155, moved up by two weeks. Mozilla does not present this change as final, but as an experiment. That is not unlike the decision made by Google with Chrome.

Firefox 155 Moves Up by Two Weeks

This information was published on July 9, 2026 by Sylvestre Ledru, Mozilla's Director of Engineering, on the dev-platform mailing list. Mozilla wants to speed up the rollout of Firefox updates (Desktop and Android) with a new 2-week cadence instead of 4 weeks. That means twice as many updates to install.

Three goals. First, shorten the wait: a ready fix that misses its train will now wait only about two weeks instead of a month. Next, make the schedule more predictable. Finally, reduce reliance on uplifts. Uplifts, what is that?

Firefox moves along release trains. Three channels advance in parallel and, at each merge day, everything shifts forward one step: what was on Nightly moves to Beta, what was on Beta ships in Release. A fix that lands on Nightly therefore takes about eight weeks to reach users (with the standard schedule). That is a long time when the bug is nasty.

An uplift is the emergency exit: the developer asks for their fix to be copied directly to Beta or Release, without waiting for the next train. That fix skips the stabilization period that is supposed to allow it to be tested and validated. Each uplift is therefore a kind of bet: ship earlier at the cost of a higher regression risk. With a departure every fifteen days, the queue is twice as short and the "this can't wait" argument will be challenged more easily.

Sylvestre Ledru is already addressing concerns. "Work that is not ready should not be rushed, and features can still take the time they need to mature." - In other words, development is not being accelerated, but rather the number of trains to the Release channel. One could also be tempted to connect this to AI speeding up vulnerability discovery: a reminder that Mozilla Firefox is scrutinized by Mythos.

Mozilla's official schedule for late August and early September is as follows:

• Firefox 154: August 18, 2026, the last version delivered on the four-week cadence
• Firefox 155: September 1, 2026, instead of the originally planned September 15
• Firefox 156: September 15, 2026
• Firefox 157: September 29, 2026

After that, there will be a major release every other Tuesday, up to Firefox 164 on January 26, 2027. One question remains: Firefox for iOS, which is not mentioned. Sylvestre Ledru describes this as an experimental change: nothing indicates that this pace will be maintained beyond January 26, 2027.

Chrome, Edge, and Firefox Now on the Same Cadence

Firefox is not the only browser adopting this new release rhythm for updates. In fact, the three major browsers will adopt this cadence at roughly the same time:

• Microsoft Edge: Edge 152, on August 27, 2026
• Mozilla Firefox: Firefox 155, on September 1, 2026
• Google Chrome: Chrome 153, on September 8, 2026

Google led the way. Back in March 2026, it announced a new Chrome release every two weeks, while keeping the enterprise Extended Stable channel at eight weeks. Microsoft followed in June. Now it is Mozilla's turn.

What This Means for the ESR Channel

Mozilla Firefox is distributed through different update channels, including the ESR (Extended Support Release) channel for enterprises. On this channel, the philosophy does not seem to change: one new version per year, with later releases bringing only security fixes. According to the official ESR schedule, the ESR 153 branch is due to open with Firefox 153 on July 21, 2026, and the ESR 140 branch will reach end of life on September 15, 2026.

However, ESR patch releases are aligned with the public release calendar. That same calendar lists ESR 153.2 on September 1, ESR 153.3 on September 15, and ESR 153.4 on September 29. The publication windows for ESR security fixes would therefore also shift from four weeks to two weeks.

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Florian Burnel Co-founder of IT-Connect

Systems and network engineer, co-founder of IT-Connect and Microsoft MVP "Cloud and Datacenter Management". I'd like to share my experience and discoveries through my articles. I'm a generalist with a particular interest in Microsoft solutions and scripting. Enjoy your reading.

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