3 Video Format Identifiers, Compared Honestly

Someone sends you an .mp4 and it will not play, or it plays with sound and no picture, or it opens on your laptop and refuses on the client’s machine. The extension told you almost nothing, because .mp4 is a container and what is inside it could be several different codecs with very different support.

That gap between extension and contents is the whole problem. A file named .mov might hold ProRes that most players cannot decode; an .mkv might hold perfectly ordinary H.264 that everything supports. Until you know the container and the codec inside it, you cannot tell whether you need a converter, a codec pack, a different player, or simply a different machine.

How to judge a video format identifier

Does it read the file or guess from the extension? Reading the header gives you the truth. Extension-based guessing gives you the label.

Does it separate container from codec? These get conflated constantly and they fail in different ways.

Does the file leave your machine? Video files are large and often confidential, and uploading a two-gigabyte rush cut to answer a compatibility question is a poor trade.

Does it tell you what supports it? Knowing the codec is HEVC is halfway; knowing which platforms play HEVC is the actionable half.

The comparison

Facts checked August 2026; plans can change.

MediaInfo Online

MediaInfo is the reference implementation for this entire category, and the online version runs the analysis in the browser using WebAssembly — so you get the authoritative answer about container format, codec, profile, bitrate, frame rate, colour space, and HDR metadata without the file being uploaded to a server or an account being needed.

Its output is exhaustive. If your question is “why will this not play on the client’s iPad”, you are reading past dozens of technical fields to find the two that matter. That is a reasonable price for accuracy.

MediaInfo desktop

The desktop application is the right tool when this is a recurring part of your work. It is free, open source, self-contained with no install dependencies, and handles many files at once — which is what you want when auditing a delivery folder rather than diagnosing one file.

For a single file that someone just emailed you, installing software is more commitment than the question deserves.

TextGround MediaInfo Online

TextGround offers a browser-based MediaInfo interface for extracting codec, resolution, bitrate, frame rate, audio channels, and tags. It is a convenient front end if you are already using that site’s other tools.

It wraps the same underlying engine on a smaller general-purpose tools site. The analysis is as good as its source; there is simply less reason to choose it over the official online version.

Video File Format Identifier

Ours works from what you know rather than from the file. Enter a video file’s name, extension, and basic properties and it identifies the likely container format and codec, and — the part the metadata readers do not do — shows which players and platforms typically support it. That last piece is usually the actual question behind “what is this file”.

The limitation is significant and worth stating plainly: because it works from details you supply rather than reading the file header, it identifies a likely format rather than the definitive one. A mislabelled file, an unusual codec inside a common container, or a variant profile will defeat it — and those are exactly the cases that cause playback failures. If you need certainty about what a file actually contains, MediaInfo reads the header and ours does not. Use ours to understand compatibility, and MediaInfo to establish facts.

Which one to pick

• If you need to know exactly what is in the file, use MediaInfo Online.
• If you inspect video files regularly or in batches, install MediaInfo desktop.
• If you are already working in TextGround’s toolset, its wrapper is convenient.
• If you know roughly what the file is and want to know what will play it, use ours.

How to do it with Video File Format Identifier

1. Open the Video File Format Identifier.
2. Enter the file name, extension, and any properties you know — resolution, source device, how it was exported.
3. Read the likely container and codec, and the platforms that typically support it.
4. Confirm with MediaInfo if the answer matters or the file is behaving oddly. More video tools are in the tools directory.

You might also need

• Video Black Bar Remover — for the other common problem with a file someone sent you.
• EXIF Viewer — for the metadata question on stills rather than video.

Frequently asked questions

Is there a free video format identifier that doesn’t need an account?

Yes — MediaInfo Online states no account and no server upload, the desktop version is open source, and ours requires no account because the site has no signup at all.

What is the difference between a container and a codec?

The container is the file wrapper that holds streams together — MP4, MKV, MOV — while the codec is how the video itself is encoded, such as H.264 or HEVC. MDN’s guide to media container formats sets out which containers commonly carry which codecs. Playback failures usually come from the codec, not the container.

Why does my .mp4 play on one device but not another?

Almost always because of the codec inside it. HEVC, VP9, and AV1 all have uneven hardware and software support, so an MP4 containing one of those can play perfectly on a recent machine and fail on an older one — while an MP4 containing H.264 plays essentially everywhere.

Final thought

Identify the codec, not the extension. The filename tells you what someone called the file; only the codec explains why a player is refusing it.

Try the free Video File Format Identifier