Microsoft Edge Dev Adds Startup Warning for Disabled Manifest V2 Extensions

There are two catches. The dialog has only been seen in Edge Dev, not Stable. And it doesn't name the extensions that were turned off.

What the new startup prompt says​

Spotted in Microsoft Edge Dev, the prompt says, "Some of your extensions were turned off" and tells users that some extensions no longer meet Microsoft Edge standards and may be removed soon. Unlike the per-extension warnings deeper in the browser, this dialog gives users a general warning and asks them to manage their extensions.

Here's what Windows Report saw:

• Two buttons: The dialog offers Manage extensions and Cancel.
• Manage extensions opens edge://extensions, where you can see which add-ons were affected.
• Per-extension cards: On that page, Edge displays a separate warning on each affected extension card. Each card says the extension no longer meets Microsoft Edge standards and may be removed soon.
• Alternatives: Each affected card has a Find similar extensions option for finding a replacement.
• The reporter's test machine: uBlock Origin and WebScrapBook were both disabled. That was one installation. It doesn't mean those two extensions are off for every user or on every channel.

The point of the change is visibility. Users no longer have to visit the Extensions page to discover that Edge has turned off some of their extensions. If your favourite add-on quietly stopped working and you never visit edge://extensions, you may simply have blamed a website.

Section summary: The Dev-channel dialog is a general alert that sends you to edge://extensions. The extension-by-extension details are still on that page.

How Edge got here​

The dialog is the last of several warnings that have appeared over the past few months.

On August 7, 2026, the Microsoft Edge team announced the consumer transition in a blog post. It said MV2 phase-out would start in August 2026, with a goal of finishing the consumer transition by the end of 2026 and enterprise deprecation following in early 2027. Microsoft also said MV2 extensions would be gradually turned off by default and that users would be notified in advance and pointed to recommended MV3 versions where they exist. The changes were set to start in Canary, Dev and Beta and then reach Stable.

Since then, Windows Report has tracked each step:

1. Canary disables MV2 extensions. Microsoft Edge Canary has started disabling Manifest V2 extensions, warning users that affected add-ons are "no longer supported in Microsoft Edge" and suggesting they "search for similar extensions".
2. Warnings in the Add-ons store. The Edge Add-ons store began showing the warning on affected listings, including uBlock Origin. A warning alone didn't mean an extension had been switched off: uBlock Origin remains enabled in Edge Canary despite the warning, so the message does not necessarily mean an extension has already been disabled.
3. Warnings in Stable. According to the outlet, Microsoft began rolling out Manifest V2 deprecation warnings on the Extensions page across Edge channels, including Stable.
4. Startup prompt in Dev. This is the new item.

Microsoft's developer timeline on Microsoft Learn (last updated September 15, 2026) lists these milestones:

Microsoft's public documents describe notices on edge://extensions and on Add-ons product pages. As far as the available evidence shows, they don't mention the startup dialog. For now, treat it as a Dev-channel observation, not a confirmed Stable feature.

Section summary: The startup prompt is one more step in a phase-out Microsoft announced in August. The schedule for that phase-out is documented. The dialog itself is not.

How many extensions are affected?​

Microsoft says very few. Its August post said 95% of the top MV2 extensions on Edge Add-ons had already moved to MV3. It counted only 58 MV2 extensions with meaningful usage, and only three of those had no public MV3 version at the time. Microsoft also said password managers, VPNs and ad blockers had moved to MV3 "with no loss of customer functionality."

Those are Microsoft's own figures and descriptions, not an independent audit. Ad blockers are the main point of dispute. Windows Forum's earlier coverage noted that under Manifest V2, extensions such as uBlock Origin can use the blocking form of the Web Request API to inspect and cancel requests dynamically. That capability is what MV3 restricts. An MV3 replacement may be fine for most people. People who rely on advanced filtering are less likely to agree that nothing was lost.

For anyone weighing other browsers, Windows Forum's earlier coverage also cited Windows Central: Brave will keep supporting the original uBlock Origin and other Manifest V2 extensions, offering Edge users a Chromium-based alternative after Microsoft completes its MV2 retirement.

What to do if the prompt appears​

Here's a sensible approach based on what has been reported:

1. Click Manage extensions, not Cancel. Cancel closes the dialog without telling you which add-ons were affected.
2. Check each warning card on edge://extensions. That's the only place you'll see which extensions were turned off.
3. Look for an official MV3 version from the same developer before using Find similar extensions. A similar extension from someone else may handle your browsing data very differently.
4. Don't count on re-enabling it. Neither Windows Report nor Microsoft's published rollout material says a disabled MV2 extension can stay usable on consumer Edge. Microsoft's stated goal is to finish the consumer transition by the end of 2026.
5. Check even if you haven't seen the dialog. It has only been reported in Dev, but the per-extension warnings are already reaching Stable. A quick look at edge://extensions will tell you where you stand.

For IT admins: separate timelines, but a firm end date​

The Dev dialog is a consumer change. Microsoft's August announcement said managed devices wouldn't be affected during the consumer rollout, and enterprise deprecation follows in early 2027. A consumer-channel prompt doesn't mean your managed Edge fleet has reached the same stage.

Microsoft's Message Center notice MC1467356, as mirrored by an independent tracker, adds detail. It names as affected parties enterprise administrators who deploy or allow-list MV2 extensions via Microsoft Edge policies (for example, ExtensionInstallForcelist, ExtensionInstallAllowlist, or ExtensionManifestV2Availability). The notice says MV2 extensions will no longer appear in Add-ons search. New installs of MV2 extensions from Microsoft Edge Add-ons will be blocked.

The most important line for admins: All migration off MV2 must be complete before the enterprise GA. After that date, MV2 extensions will not function in Microsoft Edge, and the ExtensionManifestV2Availability policy will be removed. So the policy you might use to keep MV2 extensions running isn't a long-term fix. It is scheduled to be removed.

Practical steps for admins:

• Inventory extensions by manifest version now. Windows Forum's earlier coverage made the same point: Administrators should now inventory Edge extensions by manifest version rather than wait for Stable-channel warnings.
• Contact the developers of internal and line-of-business extensions. Microsoft is asking MV2 developers to ship an MV3 version through Partner Center and has published a migration guide.
• Watch Message Center for the enterprise date. None of the materials reviewed here gives a final enterprise cutoff beyond "early 2027."

Analysis: annoying, but better than silence​

Is a startup dialog heavy-handed? A little. But the alternative is a browser that quietly switches off your ad blocker or clipping tool, after which you blame every website for loading slowly. A startup prompt is about the most direct notice a browser can give, and Microsoft did promise advance notice.

The weak spot is that the dialog doesn't say which extensions it means. "Some of your extensions were turned off" leaves people with a dozen add-ons searching through the list. Since the cards on edge://extensions already name each affected extension, it would be easy to list them in the dialog too. Maybe that will come before the prompt reaches Stable. For now it's a Dev-channel feature with no published Stable date.

The overall direction is clear. Microsoft has kept MV2 alive longer than Google did in Chrome, and it is now running out the clock in stages: warnings for developers, store labels, per-extension cards, a startup dialog, then removal. If any of your extensions still depend on MV2, start looking for replacements now.