Video Inspector

Open any video file and read its real container structure: every stream, its exact codec and profile, resolution, frame rate, language — plus why it will not play, and what to do about it. Reads MP4, MOV, MKV, WebM, AVI, MPEG-TS, Ogg and FLV. Nothing is uploaded.

Inspector Media & Files Updated Sep 24, 2026
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How to Use
  1. Drop a video file in. Nothing is uploaded — the parser reads a few kilobytes of header from your own disk, so a 4 GB file is as quick as a 4 MB one.
  2. Read the verdict first. It answers the only question that matters: is the file broken, or is it your browser?
  3. The stream list shows what is really inside — each track, its exact codec profile, and whether this browser can decode that specific track.
  4. Follow the suggested tool at the bottom if something needs fixing.

Opens the container and reads it, rather than asking the browser what it thinks — which is the whole point, because a <video> element can only describe files it can already play. Every stream, its exact codec profile, and a straight answer to why won’t this play. Nothing is uploaded, and only the header is read.

Video file
🎥
Drop a video
MP4 · MOV · MKV · WebM · AVI · MPEG-TS · Ogg · FLV

Drop a file above to read it.

Playback check — the empirical half. What the file says and what the browser actually does are not always the same thing.

How it reads a file

1 · Identify
By content, not by extension
A .mp4 that is really a Matroska file is a common cause of “it won’t play”, so the name is never trusted.
2 · Parse
Atoms, EBML, RIFF chunks
The real container tree, walked in place. Only header bytes are read, never the frames.
3 · Probe
avc1.640028, not “H.264”
The exact profile and level come out of the codec config record, then the browser is asked per stream.
4 · Play
Hand it over and watch
A browser that claims support can still refuse the file, so the claim is tested.
Speed
Independent of file size
Headers are kilobytes. A 4 GB file reads as fast as a 4 MB one.
Privacy
Nothing leaves the tab
No upload, no server round trip, no copy kept.

What it can tell you apart

Unsupported codec
The file is fine
HEVC, AV1 or a surround track your browser has no decoder for. Convert to H.264 and it plays everywhere.
Truncated file
No index found
The download stopped early, or it is one fragment of a larger recording.
Index at the end
Plays, but only after a wait
The moov atom follows the frames, so nothing shows until the whole file arrives.
DRM
Nothing can open it
Encrypted. Only the service that issued the licence keys can decode it.
Video fine, audio not
Per-stream answers
Each track is tested separately, which is why “silent video” gets a specific answer.
Wrong extension
Named by its bytes
The container is whatever the first bytes say it is, whatever the filename claims.

About the Video Inspector

Need a hand with image, audio and file tasks? The Video Inspector does the work for you — free, and right here in your browser. Open any video file and read its real container structure: every stream, its exact codec and profile, resolution, frame rate, language — plus why it will not play, and what to do about it. Reads MP4, MOV, MKV, WebM, AVI, MPEG-TS, Ogg and FLV. Nothing is uploaded.

How it works

Type in what you have, and the answer shows up right away. Change anything and it updates by itself. Everything runs in your browser, so it is fast and nothing you type is sent away.

Want the deeper story? The Knowledge Base explains the ideas behind the tools in more detail.

Frequently Asked Questions

How is this different from Video Info?

Video Info hands the file to a <video> element and repeats what it says, which only works for files that already play. This opens the container itself — the MP4 atom tree, the Matroska EBML tree, the AVI chunk list — so it can describe a file precisely because it will not play.

Why does it say my browser cannot play the video?

Usually HEVC (H.265) or a surround-sound track. Browsers ship decoders for a limited set of codecs, mostly for patent-licensing reasons rather than technical ones, and it differs between browsers and even between operating systems. The file is fine; converting it to H.264 makes it play everywhere.

What is a "codec string"?

Browsers do not answer "can you play H.264?" — they answer "can you play avc1.640028?", where those digits are the exact profile and level. This reads them out of the codec configuration record in the file and asks with the real value, so the answer is accurate rather than a guess.

What does "the index sits after the video data" mean?

An MP4 keeps its table of contents in an atom called moov. If it is written after the frames, a player must download the entire file before it can show anything. Re-saving the file moves it to the front — usually called "faststart".

It says the file is encrypted.

The file carries DRM. No tool on this site, and no browser, can decode it without the licence keys, which by design only the original service holds.

Is my video uploaded anywhere?

No. Everything runs in your browser, and only the header bytes are ever read. Close the tab and nothing remains.

How do I use the Video Inspector?

Just type your numbers. The answer shows up right away — there is no button to press. Change anything and it updates by itself.

Is it free? Does it work without internet?

Yes to both. It is free with no sign-up, and once the page has loaded it keeps working even with no internet.

Where does my data go?

Nowhere — every calculation runs on your own device. Nothing you enter is uploaded, logged, or stored.

Common Use Cases

Find out why it will not play

Separates a damaged file from a codec your browser simply does not ship — two problems with completely different fixes.

Check a download before you keep it

See the real resolution, frame rate and bitrate instead of trusting the filename.

Confirm an export came out right

Verify profile, level, bit depth and audio layout after rendering, before sending it anywhere.

Diagnose a slow-starting video

Catch an MP4 whose index is at the end, which is why it buffers forever before starting.

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