A browser-based alternative to Stellar Repair for Video

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

Stellar Repair for Video is a desktop application for Windows and macOS that repairs many video formats and offers an "advanced repair" mode that uses a sample file. FixMP4 is a narrower tool that runs in your browser with nothing to install: it focuses on MP4, MOV and M4A files whose index (moov atom) is missing or broken, the most common result of a recording cut off by a dead battery or crash, and it shows a free preview of your repaired file before you pay. If your problem is a cut-off recording from a phone, camera, drone or screen recorder, FixMP4 is a fast way to find out whether it can be fixed. If you need broad format coverage (AVI, MKV, professional formats) a desktop suite such as Stellar may be the better choice.

Side-by-side comparison

We have kept vendor-specific claims to what is publicly documented; check Stellar's site for current formats, prices and trial limits.

Where FixMP4 is the better fit

• You do not want to install software, or you are on a work computer where you cannot.
• The file is private: footage stays on your machine and the repair never uploads it.
• It is a cut-off recording: dead battery, app crash, full card, OBS crash. This is exactly the case the index rebuild is designed for.
• It is an iPhone Voice Memo or another AAC recording; FixMP4 can usually rebuild it without a reference.
• You want to know before paying: the free preview plays your own repaired file.

Where Stellar (or another desktop suite) is the better fit

• Formats FixMP4 does not support: AVI, MKV, MTS/AVCHD, MXF, ProRes, RAW formats.
• Damage inside the video data beyond a missing index, such as many scattered corrupted frames, where a vendor's proprietary heuristics may help.
• Batch processing of many files in one job.

How FixMP4 repairs a file

Most recorders write the media data first and the index last. When recording stops abruptly, the index is never written and players refuse the file. FixMP4 scans the media data, recognises each H.264 or HEVC video frame by its NAL unit structure, measures each AAC audio frame by parsing it, takes codec parameters from a reference clip recorded with the same settings, and writes a new index. Frames are not re-encoded, so quality is unchanged. More detail: fix "moov atom not found".

A practical decision path

1. Try the free FixMP4 preview first if your file is MP4, MOV or M4A and recording was cut off. It takes a minute and needs no install.
2. If the preview looks right, export with a subscription and cancel any time.
3. If the format is unsupported, or the preview shows that the damage is more than a missing index, try a desktop tool's trial and compare its preview.
4. If nothing works, the data may not be on the file at all; see recovering video from a corrupted SD card.

Reference files work the same way

Both tools benefit from a sample or reference video recorded on the same device with the same settings. The better the match, the better the result. Our guide on choosing a reference file applies whichever tool you use.

Honest limitations of FixMP4

• It does not recover deleted files or read damaged cards; use a data recovery tool first.
• It does not support AV1, VP9, ProRes, RAW, Opus, ALAC or PCM-only audio tracks.
• It cannot recreate frames that were never written or were overwritten; a hole in the data produces a short glitch.
• Very large files are processed locally, so your computer needs free disk space for the exported copy.

Common questions people ask when comparing

Is a browser tool safe for private footage? FixMP4 processes files locally with JavaScript; there is no upload step for the media. You can disconnect from the network after the page loads and the repair still runs.

Will I get the same quality? Yes. An index rebuild copies the original frames untouched; nothing is recompressed.

What does the subscription cover? Unlimited exports while it is active, for MP4, MOV, M4A and Voice Memos, with cancellation from your account page.

Does it work offline? Once the page has loaded, the repair itself runs without a network connection; signing in and exporting need one.

What if the preview fails? The diagnosis explains why, for example an unsupported codec or a file with no recoverable frames, so you know whether another tool is worth trying.

Related comparisons

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• Untrunc online alternative
• Can VLC repair video?
• All comparisons

FixMP4 compared with other options