About the author
Pritibhukhan Borah is a computer science engineer who makes videos casually, as a hobby. He maintains this site, writes the repair code and the guides, and answers the messages sent to the contact address.
Why this tool was built
One day he ended up with a corrupted video file of about 10 GB. He looked for an online tool to fix it, but the ones he found either limited the size of the file you could upload or kept the full repair behind a higher-priced subscription plan. He did not want to upload a huge private recording to a stranger's server, and he did not think fixing his own footage should cost a monthly fee.
So he built this tool. It works on a similar principle to the open-source Untrunc program: take the codec settings from a healthy video made with the same device, scan the damaged file to find every frame, and write a new index. The difference is that it runs in your browser, so there is nothing to install and nothing to upload.
Why it is free
Because the repair happens on your own computer, there is no server processing your video and no upload bandwidth to pay for. That is why there is no account, no paid plan and no size limit imposed by the tool.
How repairs are done
The repair engine is plain JavaScript. For MP4 and MOV it takes the codec settings from a healthy reference video, scans the damaged file for video frames, finds the audio between them and writes a new index (the moov box). For AVI it rebuilds the header sizes and the index from the labelled chunks in the file. Video and audio data is copied, never re-encoded. The how it works page has the technical details.
Test report
Each repair path was checked by damaging healthy recordings on purpose (removing the index, truncating the file, zeroing header sizes, overwriting bytes) and comparing the repaired file with the original. Wherever the damaged data had not been lost, the decoded video and audio were identical to the original. A step-by-step example with screenshots is in the repair demo.
Files tested
| Test file | Container and codec | Damage applied | Result |
|---|---|---|---|
| Generated clip | MP4, H.264 + AAC | Index removed | Video and audio identical to original |
| Generated clip | MP4, H.265 + AAC | Index removed | Video and audio identical to original (also repeated through the browser interface) |
| Generated large file | MP4, about 6.4 GB | Index removed | Repaired (engine run outside a browser) |
| Generated clip | AVI, Motion-JPEG | Index removed, file truncated | Repaired without a reference; decoded video identical |
| Generated clip | AVI, MPEG-4 and H.264 | Index removed, garbage inserted | Repaired without a reference |
| Generated clip | AVI | Header destroyed | Repaired using a reference AVI; a clear error is shown without one |
| Generated large files | AVI, 1.6 GB and 5 GB | Index removed | Repaired (files over 4 GB are written without an index; engine run outside a browser) |
The files above were generated for testing. Results from recordings made by specific phones, action cameras and dashcams will be added to this page once they have been checked on real devices. If a file from your device did not repair, please tell us so it can be investigated.
Browsers and devices
| Browser or device | Tested version | Result |
|---|---|---|
| Chromium, desktop (Linux, automated) | 153.0.8010.12 | MP4 and AVI repairs completed and the downloaded files decoded identically to the originals. Worked offline after the first visit. Saving through the browser's download fallback was used; the "save to disk" picker was not exercised. |
| Google Chrome, desktop (Windows) | 156.0.8078.80 | Test A (MP4 with reference), Test B (AVI without reference) and Test C (repair while offline) all passed. Repairs took a few seconds and saving worked normally. |
| Microsoft Edge, desktop (Windows) | 156.0.4314.58 | Test A (MP4 with reference), Test B (AVI without reference) and Test C (repair while offline) all passed. Repairs took a few seconds and saving worked normally. |
| Firefox, desktop | 159 | Test A (MP4 with reference), Test B (AVI without reference) and Test C (repair while offline) all passed. Repairs took a few seconds and saving worked normally. |
| Safari, desktop | 27 | Test A (MP4 with reference), Test B (AVI without reference) and Test C (repair while offline) all passed. Repairs took a few seconds and saving worked normally. |
| Samsung Internet, Android | 30.0.5.27 | Test A (MP4 with reference), Test B (AVI without reference) and Test C (repair while offline) all passed. Repairs took a few seconds and saving worked normally. |
| Safari, iPhone and iPad | 27 | Test A (MP4 with reference), Test B (AVI without reference) and Test C (repair while offline) all passed. Repairs took a few seconds and saving worked normally. |
Tested on 2026-11-03 with the sample files from the test kit: a 10.5 MB H.265 MP4 with a missing index plus a 3.6 MB reference clip, and a 2.2 MB AVI with a missing index. The tool's log in these runs showed 720 video frames and 1,408 AAC audio frames recovered (30 seconds), as expected for the MP4. Browsers, versions and devices not listed here have not been tested.
File sizes
The largest files put through the repair engine were a 6.4 GB MP4 and a 5 GB AVI, run outside a browser. The largest file repaired through the browser interface so far is about 10 MB. How large files behave in each real browser, including memory and saving, has not been measured yet, so no maximum size is claimed.
Limits you should know about
- MP4 and MOV repair needs a healthy reference video from the same device and settings.
- In MP4 and MOV, sound is kept only when it is AAC-LC.
- Frame ordering for videos that use B-frames is not rebuilt.
- MKV, WMV, MTS and professional formats are not supported.
- M4V files use the MP4 structure and are handled the same way, but were not tested separately.
Changelog
Current version: 1.1.0.
- 1.1.0, 2026-11-02: Added the guides section, the real repair demo and the test report. The file picker now lists only MP4, MOV, M4V and AVI. The save step says which format is produced (MP4 for MP4 and MOV, AVI for AVI). Collapsible menu, author information, disclaimer and contact pages. Per-format landing pages were removed.
- 1.0.0, 2026-11-01: First release. MP4 and MOV repair (H.264 or H.265 video, AAC audio) using a reference video, with streaming so there is no size limit imposed by the tool. AVI repair with automatic method selection, rebuilt header and index, and no reference needed unless the header is destroyed.
Known limitations are listed above and apply to every version.
Last updated: 2026-11-02.
Contact
Questions, bug reports or a file that will not repair? Email hello@videorepaironline.com. Please do not attach your video; describe the device, recording settings and what the tool reported, and include the technical log shown under the tool.
The repair engine uses AAC frame-detection code derived from AAC.js, licensed under the LGPL-3.0.