Rule out the two easy causes
| Cause | How to check | Fix |
|---|---|---|
| The format is unsupported | Open the file in VLC. If it plays there, the file is fine. | Use VLC, or install the codec. H.265/HEVC video needs the HEVC Video Extensions from the Microsoft Store. |
| The extension is wrong | Right-click the file, Properties, and look at the size and type. A .mp4 that is really an .mkv or a .ts fails in the Windows player. | Rename it to its real type, or play it in VLC. |
| The file is corrupt | It fails in VLC too, or VLC shows a black window or 0:00. | Repair it, below. |
Why a video ends up corrupt
Most corrupt MP4 and MOV files aren't damaged all over. They lost their index, the moov atom, because the recording stopped before the camera or phone finished the file: a dead battery, a crash, a full card, a card pulled out, or a copy that broke off. The footage is still inside. Windows can't play it because nothing tells it where the frames are.
Repair it
- Open the video in the checker on this page. The browser reads it from your disk; nothing is uploaded.
- The free check tells you whether it found the pictures and sound, and how much of the recording it can rebuild.
- Watch the free 15-second preview of your own video.
- Download the full video for $4.99, or with a plan. If the repaired video doesn't play, write to support@nasrtech.dev and we'll look at it with you.
On a PC with many files, or without a fast browser, the Video Repair program for Windows does the same offline from the Microsoft Store, $3.99 for one video. It's free to install, repair and watch the result.
What it has been tested on
We remove the index from real recordings, repair them and compare every frame with the original. Files from GoPro HERO5, 6, 7, 8 and 10, a DJI Avata, 70mai and Tesla dash cams and a Samsung Galaxy A56 came back identical, pictures and sound. In October 2026 the engine learned two layouts that had defeated it: GoPro's sound (a HERO5 file had returned 1 sound frame of 1,620) and DJI's metadata between pictures (a DJI Avata 4K60 file had returned 5 pictures of 364). Both now come back whole.
What a user wrote
"Only app that actually works and it's incredibly fast as well! Totally worth paying for the premium, and it's surprisingly cheap." (Google Play review of the Video Repair app for Android, same engine, October 2026)
