Short answer: drop the video that throws 0xc00d36c4 into the tool above and it checks the file right in your browser, telling you whether it's genuinely damaged or just missing a codec — then repairs the structural damage (truncated files, broken or missing indexes in MP4/MOV containers) when that's the cause. Nothing is sent anywhere: 0 bytes leave your device, which you can confirm yourself in the browser's Network tab. It can't recover footage that never made it into the file, and it won't alter a file whose structure is already healthy.
Test and repair the file now
Before fixing anything, find out what's wrong — that's what the drop-zone above is for. It reads the file on your machine and reports what the file really is and whether its structure is intact. Healthy structure? Then nothing needs repairing: you have a codec problem with a free fix, covered below. Broken structure? Then it's the file, and repair is the right verb. Either way you get the answer before spending a cent or a minute on the wrong branch.
Full repair for video formats is rolling out in stages: the structural remux repair (rebuilding a damaged but readable container) runs today, and reconstruction for files whose index was never written is in development. The diagnosis is the first step in both cases.
The message on your screen
Can't play. Either Windows doesn't support the item's file format, or the content doesn't match the extension in the file name. 0xc00d36c4Read it again — Windows is being unusually honest here. The dialog itself names both possibilities: a format Windows doesn't support, or content that doesn't match the file name. What it can't do is tell you which applies to your file, so most guides respond with a list of seven generic fixes to try in order. You don't need seven fixes. You need one diagnosis and then the single fix that matches.
Corrupted or unsupported — the 60-second answer
The dividing question: does the file play in VLC? VLC ships its own decoders for nearly everything, so it doesn't depend on what's installed in Windows. A file that plays in VLC is healthy. A file that fails everywhere, VLC included, is damaged.
If it plays in VLC: it's a codec problem
The file is fine — Windows just can't decode what's inside it. Three free fixes, in order of effort:
- Use VLC as your player. Free, no codec packs, done.
- HEVC Video Extensions from the Microsoft Store teaches Photos and Media Player to decode H.265 — the usual culprit for phone and drone footage.
- AV1 Video Extension, also free in the Store, covers AV1 downloads and screen recordings.
If it fails everywhere: the file is damaged
The common story is an interrupted transfer (a USB stick pulled early, a copy from a phone or camera cut short) that truncates the file and takes the index with it. The footage that did arrive is still in the file; the structure around it needs rebuilding. That's the repair the tool above performs, in your browser, without the file going anywhere.
What this can and can't fix
Repair fixes files, not Windows. If the diagnosis finds a healthy structure, the tool says so ("file structure is healthy") instead of pretending to repair a file that isn't broken, because changing a working file to route around a missing codec would damage it, not fix it. The same honesty applies to DRM-protected video, which is deliberately unplayable without its license and stays that way. What repair genuinely fixes is structural damage: truncated files, broken or missing indexes, containers whose contents no longer match their name. And missing footage — bytes that never made it into the file — can't be conjured back by any software. A failed repair is never charged.