IntactFile

Repair MP4 files — right in your browser, no upload

Most unplayable MP4s are broken containers around intact video data. Rebuild the container; keep the footage.

Your file never leaves your device — repair runs in your browser. 0 bytes uploaded.

Your data is the big block — usually intact. What breaks is the small index. Repair rebuilds it.

Drop a file here or browseTap to choose a file

ZIP · Office · PDF · video · JPG · PNG · RAR/7z · SQLite — repaired right here in your browser. Nothing is uploaded

0 bytes uploadedFree: 3 repairs/day — up to 500 MB video, 100 MB docs & archives, 50 MB photos. Free download. Single repair €5.90. No account required.

Short answer

IntactFile repairs MP4s whose container or index is broken — missing or truncated moov atoms, bad offsets, truncated transfers — by rebuilding the structure around the video data that survived. It runs entirely in your browser: the file is read from your disk locally and 0 bytes are uploaded, which you can confirm in your DevTools Network tab. The honest limit: if the footage itself (mdat) was overwritten, those frames are gone and no tool can bring them back.

Fix your MP4 now

  1. Drop the file
  2. Repair runs locally
  3. Download the result

To fix a corrupted MP4, you rebuild the parts of the file that describe the video (the container and its index) around the stream data that survived. IntactFile does exactly that, in your browser: drop the file, let the engine rebuild the structure, download the repaired copy. Nothing is installed and nothing is uploaded.

The drop-zone above does both jobs in your browser: it diagnoses the file's structure, and when the damage is a rebuildable index it repairs the MP4 right there, download included. Files whose index was never written (a recording cut off mid-save) are the one case remux repair can't cover yet; the tool tells you so honestly instead of pretending.

Why your MP4 won't play

An MP4 is two things in one file: the media data (the actual compressed video and audio, stored in a block called mdat) and the index (a block called moov that tells the player where every frame starts, how long it lasts, and how the streams line up). Nearly every "corrupted MP4" is one of two failure modes:

1. Broken index, intact data

The moov atom is written when the recording is finalized. If the camera lost power, the app crashed, or the transfer was cut short, the index is missing or truncated, but the footage in mdat is physically present. This is the common case, and it's the repairable one: the index can be reconstructed by scanning the surviving data.

2. Damaged stream data

If the bytes of the footage itself were overwritten (a failing SD card, bad sectors, a recovery tool stitching the wrong clusters), repair can rebuild the structure around the damage, but the overwritten frames are gone. No software can restore data that no longer exists in the file. A repaired file contains exactly the video that physically survived.

"Online" without uploading

"Online MP4 repair" normally means: upload your file to a server, wait, pay, download. IntactFile is online in a different sense: the tool is a web page, but the work happens on your machine. The parsing and rebuilding engine runs inside your browser tab, reading the file straight from your disk through the browser's File API. Your CPU does the repair; the result is written to your Downloads folder.

The practical difference matters most for video: a 2 GB clip takes a long time to upload before a server can even look at it, and you're trusting a copy of your footage to hardware you can't see. In-browser repair starts instantly and transmits nothing. That's not a promise, it's a mechanism, and it's verifiable in your DevTools Network tab.

What this can and can't fix

Can fix

  • Missing or truncated moov atom (unfinalized recordings)
  • Truncated files from interrupted transfers or downloads
  • Container damage: broken headers, wrong offsets, bad timestamps
  • MP4s that recovery software returned in an unplayable state, when the stream data came back intact

Can't fix

  • Overwritten mdat data — frames that no longer exist in the file
  • Damage introduced by re-encoding (the original information is already lost)
  • Encrypted or DRM-protected video
  • Files that read as 0 bytes or mostly zeros — do data recovery first, then repair the recovered file

If a repair fails, we tell you why (missing data versus broken structure), and you are never charged for a failed repair.

Common MP4 errors this solves

If you're seeing one of these exact messages, there's a dedicated page for it:

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. 0xc00d36c4

Windows Media Player / Photos — fix error 0xc00d36c4.

This file isn't playable. That might be because the file type is unsupported, the file extension is incorrect, or the file is corrupt. 0xc10100be

Movies & TV on Windows — fix error 0xc10100be.

[mov,mp4,m4a,3gp,3g2,mj2 @ 0x...] moov atom not found Invalid data found when processing input

ffmpeg and most players — fix "moov atom not found". If the file came from a crashed OBS session, see repairing OBS recordings.

FAQ

How do I fix a corrupted MP4 file for free?

Drop the file into the tool above. The free tier covers files up to 500 MB and 3 repairs per day, with a free download of the result, no account required. The repair runs in your browser, so the file is never uploaded anywhere.

Why does my MP4 file have sound but no video?

Usually one of the two streams inside the container is damaged or its index entries are wrong, so the player can decode audio but can't locate valid video frames. This is a structural problem — rebuilding the index and remuxing the streams often brings the video back, as long as the video data itself survived in the file.

Can VLC repair a corrupted MP4?

No. VLC's built-in repair only works on AVI files (the "fix the index" prompt you may have seen applies to .avi, not .mp4). VLC is still useful as a test player because it tolerates damage other players refuse, but it does not rebuild MP4 structure.

What does 'moov atom not found' mean?

The moov atom is the MP4's index — a table that tells players where every frame lives. It is written when a recording is finalized, so a crash or power loss before that moment leaves a file with data but no index. Players and ffmpeg then report the moov atom as missing. The media data usually survived; the index needs to be rebuilt. Details on the moov atom page.

Is it safe to upload my video to an online repair site?

That depends on the site, and you usually can't verify what happens to the copy on their server. The safer question is whether an upload is necessary at all: with in-browser repair it isn't. IntactFile reads and rebuilds the file locally. You can verify it yourself in the Network tab.

Can a fully corrupted MP4 be repaired?

It depends on what "fully" means. If the structure is destroyed but the stream data survived, yes — the file can be rebuilt around that data. If the data itself was overwritten, or the file reads as all zeros or 0 bytes, no tool can repair it, because there is nothing left to repair. A quick sanity check: a healthy-sized file is a good candidate; a file at 0 bytes or a fraction of its expected size usually is not.

Different symptom? Video won't play — any format or camera routes you to the exact page for your error.