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Media Doctor · Free tool

Video Codec & Format Checker

Choose a video or audio file to see what is inside: container, codecs, resolution, frame rate and audio. The checker explains compatibility risks such as HEVC or MKV and signs that a file is incomplete.

Runs in your browser. Your video is read in small pieces on this device and is never uploaded.

Check a media file

The file is analyzed on this device in a background worker. The analysis engine (about 2.6 MB) loads the first time you check a file.

Windows apps from SteveShines

Make a copy that plays everywhere

Convert, compress or rescue a file on your own PC.

QuickMedia

Video downloader and local media toolkit.

  • Converts and compresses video in its local Media Studio
  • Extracts MP3 audio, trims clips, creates GIFs and captures frames
  • Processes batches of files and keeps your media offline on your PC
Get QuickMedia from Microsoft StoreWindows app. Pricing and requirements are on Microsoft Store.

  • FixVideo

    Compress, convert to MP4 and fix playback errors.

  • CreatorCut

    Cut video, remove silence and add captions.

Why won’t my video play?

Most playback failures come from a mismatch between how a file was encoded and what the player supports. The checker looks for these causes:

  • An unsupported video codec. H.265 (HEVC) and AV1 save space but are not supported by every device, browser or editing app. Older codecs such as DivX/Xvid, MPEG-2 and WMV are rarely supported by modern browsers and phones.
  • An audio format the player cannot decode. Dolby Digital, Dolby Digital Plus and DTS often play silently in browsers and some TVs.
  • A container the player does not accept. MKV, AVI and FLV files often fail on phones, in browsers and on upload sites even when the codecs are fine.
  • An incomplete file. Interrupted downloads, copies and recordings can be cut off before their index is written, so players cannot open them.
  • The wrong file extension. A Matroska file named .mp4 confuses players that trust the extension.
  • Professional encoding settings. 10-bit or 4:2:2 H.264 and editing codecs such as ProRes need desktop software.

How to check a video’s codec and format

  1. Choose a file or drop it on the checker. It stays on your device.
  2. Wait a moment while the file’s structure is read. Large files are read in small pieces.
  3. Review the container, codecs and findings, then run the optional playback test to see whether this browser can decode it.

What the checker reports

  • Container format, file size, duration and overall bitrate
  • Video codec, profile and level, resolution, frame rate, bit depth, chroma subsampling, HDR and rotation
  • Audio codec, channels, sample rate and language, and embedded subtitle tracks
  • Compatibility warnings and signs of incomplete or malformed files, with a plain explanation of each

The most compatible video format

H.264 video with AAC audio in an MP4 container is the most widely supported combination for phones, browsers, TVs, editing apps and upload sites. If a file uses HEVC, AV1, MKV or surround audio and fails to play somewhere, converting a copy to H.264/AAC MP4 is usually the most reliable fix.

Readable metadata is not a health certificate

The checker reads headers, indexes and stream descriptions, not every frame. A file can report normal metadata and still contain damaged sections. Findings about incomplete files are labeled as suspicions, and a result without findings means no problems were found in the structure, not that every frame is intact.

Frequently asked questions

Is my video uploaded?

No. The checker runs MediaInfoLib, compiled to WebAssembly, inside your browser. It reads the file in small pieces on your device, and nothing about the file is sent to SteveShines.

Is there a file size limit?

There is no fixed limit. The checker reads only the parts of the file that describe its structure, usually a few megabytes even for very large videos, so multi-gigabyte files work. Files on slow network or USB drives can take longer.

Which formats can it check?

Common video and audio files including MP4, MOV, MKV, WebM, AVI, MPEG-TS, M2TS, WMV, FLV, MPEG, MP3, WAV, FLAC and M4A, plus many other formats MediaInfoLib recognizes.

How can I tell if a video is HEVC (H.265)?

Check the Video codec field in the results. It shows H.265 (HEVC), H.264 (AVC), AV1, VP9 or another codec, along with the profile and level when the file declares them.

Why does my video play without sound?

Either the file has no audio track, or its audio uses a format the player cannot decode, such as Dolby Digital (AC-3), E-AC-3 or DTS in a web browser. The checker shows which one applies.

Can it repair or convert my video?

No. Media Doctor only diagnoses. When the results suggest a damaged or incompatible file, the page names a SteveShines Windows app that may help, but no tool can recover video that was never written to the file.

Does “no problems found” mean my file is healthy?

Not necessarily. The checker reads the file’s structure and stream descriptions. It does not decode every frame, so damage in the middle of a file can go undetected. The optional playback test checks whether this browser can decode the beginning of the file.

Does it work on phones and tablets?

Yes, in current mobile browsers. The analysis runs in a background worker so the page stays responsive, and you can cancel it at any time.