Fix a corrupted video, whatever the format

MP4 and MOV (phones, GoPro, DJI, most cameras)

These two are close cousins and break the same way: the index (the “moov atom”) is written last, so if recording stops abruptly, the index is missing and nothing will open the file. The footage is usually still there. The fix is to rebuild the index, ideally using a good clip from the same device as a template. See how to fix a corrupted MP4 for the full process. It applies to MOV as well.

MKV (OBS, screen recorders, downloads)

MKV is more forgiving. It writes data in small self-contained chunks, so a crash usually just cuts off the end. Most players will open a crashed MKV and play up to the cut. If seeking is broken, remuxing with mkvtoolnix or ffmpeg -i broken.mkv -c copy fixed.mkv rebuilds the index. This is why OBS recommends MKV for recording: it survives crashes. Our OBS recording won’t play guide has more.

AVI (older cameras, some dashcams)

AVI keeps its index at the end. When it’s missing, VLC can rebuild it on the fly (Preferences → Input/Codecs → Damaged or incomplete AVI file → Always fix). FFmpeg can also rewrite it into a clean file.

When the damage is in the video itself

Sometimes the container is fine but the picture is not: grey blocks, smearing, green frames. That usually means part of the data was damaged on the card or during transfer. You can’t restore those frames, but you can get a file that plays smoothly around them by re-encoding. Expect the glitches to stay visible.

The one-tool route

Our repair tool detects the format and damage type for you and picks the approach. It handles MP4, MOV, MKV, AVI and more. You get a free preview to check playback before paying, and MP4/MOV files are repaired in your browser without being uploaded.

Container versus codec: the distinction that decides the fix

Every video file has two layers. The container (MP4, MOV, MKV, AVI, WebM, MTS) is the wrapper: it holds the tracks, the timing, and the index. The codec (H.264, HEVC, VP9, AV1, ProRes, MJPEG) is how the pictures themselves are compressed. Corruption can hit either layer, and the repair is completely different.

Container damage is by far the most common and the most fixable. The compressed frames are fine; the wrapper that tells a player where they are is broken or missing. Fixing it means rewriting the wrapper, which is lossless and fast.

Codec-level damage means the bytes of the frames themselves are wrong, usually from a failing card, a bad transfer, or a disk error. No tool can restore bytes that were never correctly stored. What you can do is skip the damaged frames cleanly, so the rest of the video plays without crashing the player.

A useful rule: if the file won’t open at all, suspect the container. If it opens and plays but shows blocks, smears, or freezes in places, suspect the frames.

MOV files from Apple devices and pro cameras

MOV is Apple’s QuickTime format and the ancestor of MP4. The two share the same box structure, so almost everything that applies to MP4 repair applies to MOV: a missing moov box is the usual problem, and rebuilding it from the raw data is the usual fix.

Professional cameras that record ProRes into MOV produce very large files with simple structure, which actually makes them easier to rebuild. Each ProRes frame starts with a recognisable header, so a scanner can find frame boundaries reliably even without a reference.

MOV files from iPhones may contain extra tracks for depth data, Live Photo pairing, or Cinematic mode focus information. A repair usually keeps the main video and audio and may drop these. The video will play normally; only the extra effects are lost.

MKV and WebM

Matroska (MKV) and its web cousin WebM are built differently from MP4. Instead of one index at the end, data is stored in clusters, each with its own timestamps. If recording stops abruptly, everything up to the last complete cluster is normally playable. This is why OBS recommends MKV for recording.

When an MKV won’t open, the damage is usually in the header at the start, or the file ends mid-cluster and some players refuse it. Remuxing with FFmpeg (ffmpeg -i broken.mkv -c copy fixed.mkv) or MKVToolNix rewrites the header and cues and fixes most cases.

If you need an MP4 for editing, remux to MP4 after the repair: ffmpeg -i fixed.mkv -c copy fixed.mp4. This works as long as the codecs are MP4-compatible, which H.264, HEVC, and AAC all are. Opus or Vorbis audio may need re-encoding to AAC.

AVI and older formats

AVI has an index called idx1 at the end of the file, similar in spirit to MP4’s moov but much simpler. When it is missing, many players refuse to seek or refuse to play. VLC offers to rebuild the AVI index when you open such a file; accept, and it will build one in memory so the file plays.

To fix the file permanently, remux it: ffmpeg -i broken.avi -c copy fixed.avi writes a new index. Older tools such as DivFix++ and VirtualDub do the same and are still useful for very old files.

AVI files from cheap dashcams and older digital cameras often use MJPEG, where every frame is a complete JPEG. That makes them very robust: even heavily damaged files can be cut around the broken frames with little loss.

MTS, M2TS, and AVCHD camcorder footage

Camcorders from Sony, Panasonic, and Canon often record AVCHD: MTS files inside a folder structure with PRIVATE/AVCHD/BDMV/STREAM. MTS is a transport stream, a format designed for broadcast that repeats its setup data constantly. It is very forgiving, and a truncated MTS usually plays up to the point it was cut.

The common problem is not corruption but copying only the MTS files without the rest of the folder, which loses the clip metadata that joins long recordings split across files. Copy the whole AVCHD folder, and open it in software that understands the structure, or join the MTS files with ffmpeg -i "concat:00000.MTS|00001.MTS" -c copy joined.mts.

WMV, FLV, and 3GP

These formats are less common now but still turn up in old archives. WMV uses the ASF container with a header at the start and an optional index at the end; a missing index affects seeking more than playback, and remuxing fixes it. FLV, from old Flash-era downloads, has a small header and per-tag timestamps, and FLVMeta or a remux usually repairs a missing duration. 3GP, from older phones, is a simplified MP4 and can be repaired the same way.

For long-term safety, convert repaired files in these formats to MP4 with H.264, which plays everywhere. That step is a re-encode and loses a little quality, so keep the repaired original too.

Checking whether the file is really corrupted

A surprising number of files reported as corrupted are perfectly fine and simply can’t be decoded by the player at hand. Before repairing anything, try VLC or MPV, both of which bring their own decoders.

Windows Films & TV and Photos need a paid or free extension for HEVC, and many older Windows installs lack AV1 support. macOS QuickTime refuses MKV, AVI, and most WebM files entirely. Smart TVs often reject 10-bit HEVC or high bitrates. A file that plays in VLC on the same machine is almost certainly not corrupted.

Use ffprobe file to see the container and codecs. If everything listed looks sensible and ffmpeg -v error -i file -f null - runs without errors, the file is healthy and the fix is a different player or a conversion, not a repair.

Salvaging partly damaged footage

When a file has genuinely damaged frames in the middle, your goal changes from fixing everything to saving as much as possible. First, play the file in VLC and note the timestamps where trouble starts and ends.

Then cut out the healthy sections losslessly: ffmpeg -ss 00:00:00 -to 00:03:12 -i in.mp4 -c copy part1.mp4 and ffmpeg -ss 00:03:20 -i in.mp4 -c copy part2.mp4. Lossless cuts snap to keyframes, so the result may include a second or so more or less than requested. Join the parts if you want a single file.

If the damaged region is small and you need continuous footage, re-encoding the whole file lets the decoder conceal errors by repeating nearby frames. The result looks smoother than a hard cut but costs some quality and time.

Preventing the next corrupted video

Most corruption comes from interrupted writes: power loss, ejected cards, app crashes. Use fragmented or crash-safe recording formats where available (MKV or hybrid MP4 in OBS, fragmented recording settings on some cameras). Stop recording and wait a moment before switching off.

Copy footage off cards promptly, verify the copy plays, and only then format the card in the camera. Formatting in the camera rather than on a computer keeps the file system the way the camera expects it.

If you need a repair now, open the repair page. It identifies the container, chooses a lossless remux or an index rebuild, and shows a free 15-second preview. Unlock the full file for $9/month or $29/year. For MP4-specific steps, see fix a corrupted MP4.

Symptoms and likely causes at a glance

Won’t open, any format: missing or broken header or index. Usually fully repairable.

Opens with zero duration: the container never recorded its length. Remux or index rebuild.

Plays, then stops early: truncated file or index covering only part of the data. Rebuild from raw data, and check for a longer original.

Grey or green blocks that spread until the next scene change: damaged frames. Cut around them or re-encode with error concealment.

Black picture with sound: missing video codec setup, or an unsupported codec on this player. Try VLC; if VLC also shows black, rebuild with a reference clip.

Sound with clicks, gaps, or a robotic tone: damaged audio packets or wrong audio format in the rebuilt index. Re-run the rebuild with a correct reference, or replace the audio with a clean re-encode.

Plays too fast or too slow: wrong timescale. Remux with regenerated timestamps, or set the frame rate explicitly.

Corrupted videos after transfer or download

If a video broke during a copy, upload, or download, the original may still be fine. Check the source first: re-download from the cloud, copy again from the card, or ask the sender to share it through a link rather than a chat app.

Cloud sync tools sometimes leave placeholder files that look like videos but contain no data until fully downloaded. On OneDrive and iCloud Drive, make sure the file is marked as available offline before working on it. A partial download is effectively a truncated file and is best fixed by downloading again.

Files moved between FAT32 drives silently fail beyond 4 GB. If a big video is exactly 4,294,967,295 bytes, the rest was cut off by the file system, and the missing part only exists on the original drive.

Choosing between doing it yourself and using a service

If you have one file, a few minutes, and you’re comfortable with a terminal, the free tools covered on this page will fix most container damage. If you have many files, an unusual camera, or a file that free tools couldn’t fix, a dedicated repair saves time.

Our repair page checks the file, tries a lossless remux, a native frame-level rebuild, and a reference-based rebuild, and reports which worked. You watch a free 15-second preview first and only pay ($9/month or $29/year) if you want the full file. Related guides: how to repair corrupted video files and how to uncorrupt a video file.

How long to spend on a repair yourself

A sensible budget for DIY repair is about half an hour. In that time you can install VLC and FFmpeg, identify the container, try a remux, and see whether the file needs an index rebuild. If you’re past that point and still stuck, the problem is usually one that needs a specialised rebuild or a reference clip, and a dedicated tool will be faster.

Keep notes of what you tried. If you hand the file to a tool or a person later, knowing that a remux failed with a missing-index error saves them repeating the same steps.

And whatever you try, keep the untouched original. Every repair attempt should read from it and write to a new file, so a failed attempt never costs you anything.

Fixing corrupted video from different devices

Where a video came from shapes how it breaks. Phones tend to produce clean files that only lose their index when the app crashes or the battery dies. Action cameras and drones record to memory cards that are often removed quickly, so incomplete writes are common. Screen recorders and game capture tools can leave files without an ending if the program is force-closed. Security cameras and dashcams loop over old footage and may leave fragments.

Knowing the source helps you choose the right reference file and set expectations. A phone clip interrupted by a dead battery is usually fully recoverable, while a dashcam fragment from an overwritten loop may only give back a few seconds.