TidyToolsWhy the date on your computer is usually wrong
Your file manager shows two dates: created and modified. Both describe the file, not the recording. Copy a video from a phone to a laptop and the created date becomes today. Move it to a USB stick, restore it from a backup, download it from a chat app — same thing. Within a couple of hops the original date is gone entirely.
The camera, meanwhile, wrote the real moment of recording into a small block of data inside the file itself. That block travels with the video wherever it goes, and nothing you do in Windows or macOS touches it. This tool reads that block and shows you what it says.
When the recording date is wrong too
Occasionally the date inside the file is also nonsense — every clip claiming 1 January of some year, or a date that clearly isn't when you were there. That almost always means the camera's clock had been reset. Action cameras and older compacts keep time with a small internal charge, and taking the battery out for a while wipes it. The camera then starts counting from its factory default and stamps every recording with a date that never happened.
If you suspect that, the giveaway is the content: check whether the footage matches the season the date claims. A clip stamped February showing a lake and bare shoulders is a reset clock, not a winter swim.
Why a video won't play
An MP4 is made of labelled sections. The footage itself lives in one called mdat, and the index that tells a player where each frame sits lives in another called moov. Most cameras write the footage continuously while recording and only add the index when you press stop.
That ordering explains the most common failure of all. If the battery dies mid-recording, or the memory card is pulled, or the camera crashes, the footage is safely written but the index never is. You end up with a large file that no player will open — and it feels like the video is gone, when in fact almost all of it is there. The tool tells you when that has happened, and those files are usually repairable with a free utility called untrunc, which borrows the index structure from a working clip shot on the same camera at the same settings.
The other failure: an index that doesn't match
A second pattern looks stranger. The player shows the right duration, the scrub bar is full length — and then it jumps straight to the end without showing anything. That means the file has an index, but the frames aren't where it says they are.
This is the signature of a file that has been through recovery software. Video files are often stored in scattered pieces across a drive, and when recovery tools reassemble them they sometimes get the order wrong. What comes out looks like a complete video and is structurally valid, but the picture data is nonsense. The tool checks a spread of positions against the index and tells you if they disagree.
Frequently asked questions
Is my video uploaded anywhere?
No. The file is read directly by your browser using ordinary file APIs and never leaves your device. There is no server involved, no account, and nothing stored. You can disconnect from the internet and this page still works.
Does it work on large files?
Yes. It reads only the index and a handful of small checks scattered through the file, so a four-hour 4K recording is checked as quickly as a ten-second clip. Nothing is loaded into memory whole.
Which formats are supported?
The MP4 family: .mp4, .mov, .m4v, and GoPro's .lrv preview files. That covers phones, action cameras, drones and most modern cameras. AVI, MKV and WMV use a different structure and aren't read.
Why does it say "no recording date"?
Either the file has no index at all — meaning the recording was cut short — or whatever created it never wrote one. Files exported from editing software often carry the export date rather than the original recording date, and screen recordings frequently have none.
Can it repair a broken video?
No, and it won't pretend to. It identifies what is wrong and names the right tool for the job. Diagnosing correctly is most of the work — knowing whether footage is missing or merely unindexed decides whether repair is worth attempting at all.
Why does the duration differ from what my player shows?
The duration here is read from the file's own index. If a player shows something different, it is usually estimating from file size and bitrate — which is what players fall back on when the index is missing or unreliable.