Repair a corrupted video in your browser (no upload)

By the FixMP4 engineering team · Updated October 9, 2026 · Tested on real H.264, HEVC and AAC recordings

A corrupted video is one of the most stressful things that can happen to a recording. The file is there, it even has the right size, but every player refuses to open it. VLC shows nothing, QuickTime says the file "could not be opened", Windows Media Player reports an unsupported format and your editor throws an error. The good news: in most cases the actual pictures and sound are still inside the file. What is broken is the small table of contents that tells a player where those pictures and sounds are. FixMP4 rebuilds that table of contents directly in your browser, so you can repair a corrupted video without uploading it anywhere.

Open the free repair tool and drop your file. You will see a free 15-second preview of the repaired video before you decide to pay for the full export.

Why videos get corrupted

MP4 and MOV files are built from boxes (also called atoms). The two that matter most are:

• mdat, the media data: the compressed video frames and audio frames, written continuously while you record.
• moov, the index: frame sizes, timestamps, keyframe positions, codec settings and the exact byte position of every frame.

Most cameras, phones, drones and screen recorders write the media data first and the index last, when you press stop. If the recording ends any other way, the index is never written. Typical causes are:

• the battery died while recording,
• the phone or camera crashed, froze or overheated,
• the memory card was removed or ran out of space,
• the recording app was killed by the system,
• a file copy or download was interrupted halfway,
• a sector at the start of the file was damaged, wiping the header.

In all of these cases you get the same symptom: a file full of valid video and audio that no player can read, often with the error message "moov atom not found".

How FixMP4 repairs a corrupted video

FixMP4 does not "guess" at your footage and does not re-encode it. It reads the raw data and writes a brand new, correct index around it:

1. Diagnosis. The tool walks through the boxes of the file and reports what is wrong: missing index, truncated media data, damaged header or a box structure that breaks at a specific byte.
2. Reuse what survived. If an index is still present (for example when only the header was wiped, or when a "fast start" file was cut short), the tool keeps it, drops the entries that point past the end of the file and writes a clean header.
3. Rebuild what is missing. If the index is gone, the tool takes the codec settings from a healthy reference file recorded by the same device, then scans the media data and identifies every single frame. Video frames are found through their H.264 or HEVC structure, audio frames by walking the AAC bitstream. Frame order is decoded from the video itself so that B-frames play back in the right order.
4. Write a playable file. A new MP4 or MOV is assembled: a fresh header, the rebuilt index and your original frames, bit for bit.

Because the media is copied rather than re-encoded, the quality of the repaired video is identical to the original recording.

Why a reference file helps

Video codecs store their settings (resolution, profile, the H.264 SPS/PPS or HEVC VPS/SPS/PPS parameter sets) in the index. When the index is gone, those settings are gone too. A short healthy clip recorded by the same device with the same settings contains exactly the same settings, so FixMP4 copies them from it. Good reference files:

• come from the same phone or camera,
• use the same resolution and frame rate (for example 4K 30 fps),
• use the same mode (HDR on or off, the same "most compatible" or "high efficiency" setting on iPhone),
• play normally.

For audio-only recordings such as iPhone Voice Memos, a reference is optional: FixMP4 can usually detect the AAC stream on its own.

What you get for free, and what is paid

• Free: unlimited diagnosis and a repaired 15-second preview that you can play right on the page. This proves the repair works on your file before you pay anything.
• Paid ($9/month or $29/year, cancel anytime): export of the full repaired file, as many files as you like while your plan is active.

We designed it this way because the biggest complaint about video repair software is paying first and discovering afterwards that the file still does not play.

Your video never leaves your device

Everything happens inside your browser tab. The file is read locally, repaired locally and saved locally. Nothing is uploaded to a server, which also means there is no upload limit and no waiting for gigabytes to transfer. This matters for private recordings, client footage and anything covered by an NDA.

What can and cannot be repaired

Supported today:

• MP4, MOV and M4A files with H.264 (AVC) or HEVC (H.265) video and AAC audio, which covers iPhone, most Android phones, GoPro, DJI, many dashcams and OBS recordings to MP4.
• Missing or deleted moov atom ("moov atom not found").
• Recordings cut off by a dead battery, a crash or a full card.
• Files whose header bytes were zeroed or overwritten.
• Fast-start files whose end is missing.
• Short damaged regions inside the media data: the tool skips them and continues with the next keyframe.

Not supported (yet):

• ProRes, MPEG-2, MPEG-4 Part 2, AV1 and VP9 video; PCM, ALAC, Opus and AC-3 audio.
• Fragmented MP4 recordings and encrypted (DRM) files.
• Frames whose own bytes are damaged: the tool can rebuild the index, but it cannot restore pixels that were overwritten.
• Files that were never written at all, for example a 0-byte file or one filled entirely with zeros.

If your file falls outside this list the free preview simply will not work, and you will not be asked to pay.

Step by step

1. Open the repair tool.
2. Drop the corrupted video into the left box.
3. Optional but recommended for video: drop a short healthy clip from the same device into the right box.
4. Press Repair and watch the free preview.
5. If it looks right, subscribe and export the full file.

Need more detail on a specific error? Read our guides on fixing "moov atom not found", repairing MP4 files, repairing MOV files and videos that won't play after recording.

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