Windows 11 25H2 (build 26200): right-click menu takes 1-2 seconds to open — how do I tell if it's a shell extension or Windows itself? Whose Fault?

Split the problem in two before you touch anything, because Windows 11 has two menus and they don't load the same things.

The short menu surfaces commands from apps that register them the modern, packaged way. Old-style COM verbs — the ones every installer has been dumping into the shell for twenty years — get pushed down under "Show more options". So:

• if only "Show more options" is slow, you're paying for legacy handlers and there will be a lot of them
• if the first menu is slow too, look harder at the item you're right-clicking than at your extension list

Then vary the target rather than the machine. Right-click a file in a plain local folder, then one inside a cloud-synced folder, then one on a mapped network drive. A sync provider or a half-dead mapped drive will stall the menu while the shell asks about status, and that has nothing to do with extensions at all. A mapped drive pointing at something that no longer exists is the classic: it blocks for the full SMB timeout, every single time.

You already said desktop is fastest and normal folders are slower, which reads more like per-item work than a global handler.

On the rebuild everyone keeps mentioning: what exists right now is reporting, not a shipped feature, and it's worth being precise about that before you plan around it.

The consistent version across the coverage is a more compact menu that prioritises the commands people use most instead of loading every third-party entry up front, plus a built-in way to show, hide and reorder items so people stop editing the registry to get what they want. It was apparently demonstrated at an Insider meetup rather than announced, it has not appeared in an Insider build, and the timing being quoted is "before the end of the year" with no official date attached.

Practical read: the described mechanism is "don't load third-party commands until asked", which is exactly what you can approximate today by finding the handler that's slow and removing it. Do that, and treat the redesign as a nice surprise if it lands.

Even with only Defender in play, real-time protection touches files while the shell enumerates them, and on spinning rust or an ageing SSD that shows up as exactly this kind of first-hit-is-slow, next-few-are-fast pattern — which is also what a cache warming up looks like, so it's worth separating.

Cheap measurement: temporarily exclude one test folder, copy a handful of files into it, and right-click there. If that folder is suddenly quick and an equivalent non-excluded folder isn't, you know where the time is going and you can decide whether you care. Then remove the exclusion. I'm not suggesting you leave a hole in your scanning, only that it's a clean five-minute experiment with a clear undo.

Bisecting is still the honest answer, and it's quicker than it sounds because you halve the search each round.

Context menu handlers are COM objects loaded into explorer.exe. NirSoft's ShellExView and ShellMenuView enumerate them and let you disable non-Microsoft entries without hand-editing the registry. Sort by company, disable everything that isn't Microsoft, restart Explorer, test. Fast now? Re-enable half, test again. Three or four rounds and you have a name.

Two cautions. Don't bulk-disable Microsoft-signed entries. And restart the shell between rounds — Task Manager's restart option, or taskkill /f /im explorer.exe then start explorer — otherwise you're testing a stale explorer.exe that still has the old handler mapped.

If you'd rather not install anything: create a fresh local user account and right-click there. New profile, most per-user handlers gone. Fast in the new account means it's something in your profile. Still slow means machine-wide, or the item itself.

Free interim move while you hunt: hold Shift when you right-click, or press Shift+F10 from the keyboard with the item selected. That takes you straight to the full menu and skips the two-step entirely.

It makes nothing faster. But if a decent share of your irritation is the extra hop into "Show more options", it removes that share today with nothing to undo later.

Easiest fix: put the classic menu back with the registry key. Menu becomes instant, problem gone. Been running mine that way for ages.