Media File Inspector

about this tool

Drop a file and find out what is actually in it. There is an EXIF viewer here for images and nothing equivalent for media: the audio trimmer and the video converter both change a file, and neither tells you what it holds.

The question is usually "why will this not play"

And the answer is usually the codec, not the file.

A container — MP4, MKV, WebM — is a wrapper. The codec inside it is a separate thing. A file can be a perfectly valid MP4 and still be undecodable in the browser you are holding, because H.265 plays in Safari and not in Firefox.

So every track is asked directly whether this browser can decode it, and the answer is shown per track. That is a more useful fact than the codec name on its own, and it is the one nothing else on the page will tell you.

Sideways video

Phones record in landscape and add a rotation flag rather than turning the pixels. Players that honour the flag show it upright; players and converters that ignore it show it on its side.

When the stored size and the intended display size differ, both are shown, so you can see which one a piece of software is likely to have used.

What it reads

Container and MIME type, duration, overall bitrate. Per track: codec and full codec string, bitrate, language and name. For video: display and coded size, aspect ratio, frame rate, colour space, whether it is HDR and whether it can carry transparency. For audio: channels and sample rate. Plus any title, artist or comment tags the file carries.

MP4, MOV, WebM, Matroska, WAV, OGG, FLAC, MP3, AAC and MPEG-TS.

It does not decode the file

Only the container headers and enough packets to work out a rate. A two-hour film is read as fast as a two-second clip.

Nothing is uploaded

The file never leaves your browser — it is read straight off the disk. That is worth stating plainly for this one, because the files people drop into a media inspector are usually personal: recordings, footage from a phone, work that has not been released.

The library that reads the formats is fetched when you drop a file rather than when the page loads, because it is not small and most visitors to the site will never open this page.

For the same question about an image, the EXIF viewer reads what a camera wrote. To change what you find here rather than only read it, video to GIF, trim & convert and the audio trimmer both work in the browser too.

questions

Why will this video not play in my browser?

Almost always the codec rather than the file. A container like MP4 or MKV is just a wrapper, and the codec inside it is a separate question — H.265 plays in Safari and not in Firefox. Each track here is asked directly whether this browser can decode it.

What is the difference between a container and a codec?

The container is the file format that holds the tracks — MP4, MKV, WebM. The codec is how each track is compressed inside it — H.264, AAC, Opus. A player can support the container and still be unable to decode what is in it.

Why is my video sideways in some players?

Phones record landscape and add a rotation flag rather than rotating the pixels. Software that honours the flag shows it upright; software that ignores it shows it on its side. The tool reports the stored size and the intended display size separately when they differ.

Is a large file uploaded anywhere?

No. The file is read in your browser, and only the container headers and the first few packets are touched — a two-hour film is read as fast as a two-second clip, and nothing is sent anywhere.

Which formats does it read?

MP4, MOV, WebM, Matroska, WAV, OGG, FLAC, MP3, AAC and MPEG-TS.