How to check whether a video file is corrupted on a Mac

Q: Can I check a batch of files at once?

In Terminal, file .mp4 in the folder reports every file in one go and immediately flags any that show as "data". For a deeper check, drop the whole batch into Manatee's Repair; each file gets its own outcome in the job list, and nothing is modified.

23 August 2026 · 6 min read

The fastest check is to select the video in Finder, press Command-I, and look at the size: if it is 0 bytes or far smaller than it should be, it is truncated. If the size looks right but QuickTime Player refuses it, open it in a player that bundles its own decoders; a file that plays there is healthy and merely in a format QuickTime lacks. A file that fails in both, or plays but freezes, skips, or stops early, is corrupted, and the checks below tell you how badly.

Check one: the size in Get Info

Select the file in Finder and press Command-I. Look at the Size line.

Zero bytes. The file is a name with nothing behind it. No repair can work on it. See video-file-is-0-bytes-or-shows-the-wrong-length-can-it-be-fixed.
A few kilobytes for what should be minutes of video. Only the header was written. Effectively the same as zero.
Suspiciously round. Exactly 4 GB (4,294,967,295 bytes or thereabouts) means it hit the size limit of a FAT32-formatted card or drive and was cut off there. The content up to the cut is usually recoverable.
Plausible. A phone video runs roughly 100 to 400 MB per minute at 4K, 60 to 130 MB per minute at 1080p. A dashcam or action camera is similar. If the number is in the right range, the content is probably on disk and any problem is structural.

If you have the source (phone, camera, sender), compare the sizes. A different byte count on the copy means the transfer was incomplete.

Check two: what QuickTime and Quick Look say

Press the space bar with the file selected. Quick Look reads the file’s index and shows a preview with a duration. Then double-click to open it in QuickTime Player.

Quick Look shows a thumbnail and a sensible duration, QuickTime plays it through. Not corrupted.
Quick Look shows a generic icon, QuickTime says the file is not compatible or could not be opened. Either the index is missing (corruption) or the format is unsupported. Check three separates these.
Duration shows as 0:00 or something absurd like 72 hours for a two-minute clip. The index is damaged. The frames may be fine.
Plays, then freezes or jumps partway. Damage in the middle of the file: a bad sector, a dropped stretch during transfer. The parts on either side are likely intact.
Audio plays but the picture is black. The video track is damaged or unsupported while audio is fine. See how-to-fix-a-video-that-plays-audio-but-shows-a-black-screen.

QuickTime’s error messages are not diagnostic on their own. “Not compatible” is what it says for both a perfectly good MKV and a damaged MP4.

Check three: a player with its own decoders

QuickTime relies on the codecs built into macOS. An open-source media player ships with decoders for nearly everything and is far more tolerant of structural damage. Open the file there.

Plays normally. The file is intact. Your Mac simply cannot play that format natively. Convert it to MP4 and the problem ends; container-vs-codec-why-an-mp4-can-still-refuse-to-play explains why this happens so often.
Offers to repair the index, or plays with glitches. The file is damaged but has recoverable content.
Refuses, or shows nothing. Significant damage. Move to the next check before giving up.

This single check settles the most common confusion: a file that is not corrupted at all, just unfamiliar to QuickTime. WEBM, MKV, AVI, and HEVC-in-MP4 from some cameras all land here.

Check four: look at the first bytes in Terminal

If you want a definite answer about what the file is, Terminal can read the first few bytes without opening the video. Open Terminal and type the following, dragging the file onto the window instead of typing its path:

file followed by the path. Press Return. A healthy MP4 reports something like “ISO Media, MP4 Base Media” and a MOV reports “Apple QuickTime movie”. If it reports “data”, the header is unrecognizable: either the file is damaged at the start or it is not a video at all.
xxd followed by the path, then | head -2. The first line of a healthy MP4 or MOV contains ftyp a few bytes in. An MKV or WEBM starts with the bytes 1a 45 df a3. An AVI starts with RIFF. Nothing recognizable means a damaged or misnamed file.
tail -c 64 followed by the path, then | xxd. For MP4 and MOV, a file that was properly closed usually has recognizable atom names near the end. A tail of all zeros, or random bytes, suggests the file was cut off.

None of this changes the file. It is read-only and safe to run on the only copy you have.

Check five: let a repair engine tell you

The most complete diagnosis is to attempt a repair and read the report, because the repair engine has to parse the entire file to do its job. With Manatee, that is a drag-and-drop that costs nothing and touches nothing:

Open Manatee and choose Repair.
Drop the video in (or right-click it in Finder and choose Fix with Manatee).
Read the outcome. Fixed means the structure was damaged but the content was complete, and a working copy has been written next to the original. Partial means some content was missing, with a statement of what was recovered, for example the first eleven minutes. Not fixable means no usable frames were found.

The original file is never modified; Manatee always writes a new copy alongside it. So even if you only wanted a diagnosis, you have lost nothing, and if the answer was Fixed, you are done.

Be clear about what this does not cover. Manatee cannot diagnose a failing drive or card (if the same file gives different results on different reads, the storage is the problem), and it does not recover deleted files. If the video was deleted rather than damaged, a repair tool is the wrong category entirely.

Before you fix anything

Whatever the checks show, do two things first:

Make a copy of the file on a different drive and work on the copy.
If the file came from a device, confirm whether the original is still on it. A fresh copy from the source beats any repair.

Then, depending on the diagnosis: convert a healthy-but-unsupported file to MP4; repair a file with a broken index or a truncated tail; and accept that a 0-byte file or one whose frames were never written has nothing to give.

Questions

The file plays fine on my iPhone but not on the Mac. Is it corrupted?

No. If it plays anywhere it is intact. The iPhone records HEVC by default and some Macs and apps handle it less gracefully. Convert to H.264 MP4 or see iphone-video-won-t-play-on-mac-after-airdrop-why-and-how-to-fix-it.

Can I check a batch of files at once?

In Terminal, file *.mp4 in the folder reports every file in one go and immediately flags any that show as “data”. For a deeper check, drop the whole batch into Manatee’s Repair; each file gets its own outcome in the job list, and nothing is modified.

The video plays but the last few seconds are missing. Is that corruption?

Usually it is an unfinished write: the recording stopped before the camera flushed the final seconds to storage. Those seconds were never on disk. The file itself may be structurally fine, and there is nothing to repair.