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Extension Pulse, week of August 17: Edge starts killing MV2, Firefox goes fortnightly

Edge starts phasing out MV2. Firefox 155 goes fortnightly. Chrome 153 binds protocol handlers to the extension lifetime.

Maxim Kosterin
4 min read
Two overlapping hairline circles with orange watercolor only in the intersection — Edge and Firefox catching up.
Two overlapping hairline circles with orange watercolor only in the intersection — Edge and Firefox catching up.

The last Chromium browser that was still polite about Manifest V2 stopped being polite.

Microsoft's Edge blog, August 7: MV2 starts turning off in Canary / Dev / Beta immediately. Consumer Stable "complete by end of 2026." Enterprise early 2027. They say 95% of top MV2 items on Edge Add-ons already moved to MV3, and only 58 MV2 extensions with meaningful usage remain — three without a public MV3 replacement.

That's the escape hatch closing. Chrome already yanked runtime (150) and flags (151) and is about to yank the store (August 31). Hoping "we'll just tell users to install the Edge listing" was a strategy. It has a date now.

I wouldn't treat "end of 2026" as a soft maybe. Canary is already the experiment. Stable is a policy meeting away.

Firefox is about to ship like Chrome

Firefox 154 (August 18) is the last monthly. 155 Beta started August 13 and the train becomes two weeks. Stable ~September 1, then every fortnight after that.

If your QA process is "we test each Firefox once a month," it is now twice a month whether your calendar says so or not. ESR (153) is the slow lane; everyone else is on Chromium's cadence.

154 also ships the sandbox key I wrote up last week. Don't miss that in the noise of the cadence change.

Stable September 8. The ones I'd keep:

  • Protocol handlers follow the extension. Register web+foo:, disable the extension, handler goes away. Uninstall, gone. No more orphan protocol handlers surviving the extension that owned them (CL 8259429).
  • chrome.cookies obeys user site restrictions. If the user blocked or withheld a site, the cookies API doesn't get a back door (CL Ic46119d4). Long overdue, and it will break extensions that treated "I have the cookies permission" as "I have every cookie."
  • URLPattern path matching handles UTF-8. Non-ASCII match patterns stop being quietly wrong (CL 8258871).
  • chrome.tabs.create({ splitWithTabId }). Split-view is an API now, not a user gesture you can't automate.
  • Native messaging infrastructure for Android (NativeMessageAndroidPort). Infrastructure CL, not "your Android extension can talk to a host tomorrow," but the rails are going in.
  • webRequest event dispatch moving C++ → JS. Listener registration and detail-filters in JS. Internal; watch it if you do exotic filtering.

WECG #326 closed: the "tab" context type in contextMenus is now in Chrome, Firefox, and Safari. Right-click on a tab, cross-browser. That's a ten-year "works in mine" bug becoming a sentence you can put in a README.

#1056 proposes deprecating runtime.getPlatformInfo().nacl_arch (NaCl is dead; the field is a fossil, and MIPS/MIPS64 are misnamed for LoongArch). Needs-triage. Don't start new code on nacl_arch.

What I'd do this week

Edge MV2: submit the MV3 package to Partner Center this month, not in December. The Manifest V3 generator plus @extenshi/cli is the same drill as Chrome. Five scans/month free; prepaid packs after.

Firefox: put 155 Beta on the CI matrix. Fortnightly means your "we'll catch it next cycle" is fourteen days, not four weeks.

Chrome 153: audit chrome.cookies against sites the user can lock you out of. If your cookie reader assumes <all_urls> forever, 153 is a production bug.

August 31 CWS MV2 purge is two weeks out. The June catalog count is the reading if you still think this is theoretical.

Sources

Methodology

Signals dated 2026-08-10 through 2026-08-17. This week had no Listmonk draft (the Monday generator ran dry or the notes landed after send); the blog issue is backfilled from the same signal window so the series doesn't have a hole. Chrome 164 schedule folded into the 153 story.

This issue of Extension Pulse is compiled from the Edge blog, Mozilla's calendar, Chromium Gerrit, WECG issues, and Extenshi catalog snapshots. We don't independently verify every upstream claim. If something here is off, tell us at [email protected].

Last week's Pulse → · Browse the catalog →

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