About this tool
Separate binary container evidence from browser claims and metadata availability before using a media file in a publishing or support workflow.
Media Metadata Inspector answers a narrow but common question: does this audio or video file actually contain what its name and browser MIME type claim, and what can the current browser learn about it without a full decode? It reads the file's binary signature with the file-type library, compares that detected container against the filename extension and the MIME string the browser attached, and then asks the browser's own media element to load metadata for up to 15 seconds. From that it reports duration, video width and height, a reduced aspect ratio, and a whole-file bitrate estimate calculated by dividing total bytes by duration. Findings are listed in plain language and the entire result can be downloaded as a JSON report.
- Uses file-type 22.0.1 signature evidence before browser MIME claims or filename extensions to classify supported audio and video containers.
- Runs a cancelable 15-second browser metadata probe for duration and video dimensions, then derives aspect ratio and an explicitly labeled whole-file bitrate estimate.
- Exports versioned JSON with signature, claim comparison, browser support, probe errors, derived values, findings, and every unsupported assurance set to false.
How to use Media Metadata
Click the file picker and choose one audio or video file up to 200 MB; the accept list covers common containers such as MP4, MOV, MKV, WebM, MP3, FLAC, and WAV. Press Inspect metadata. The Detected container section shows the signature result, the extension the filename carries, and a MIME comparison labeled match, mismatch, not supplied, or not detected. The browser section then fills in Duration, Dimensions, Aspect ratio, and Whole-file bitrate as the probe completes; a Cancel button stops a probe that is taking too long. Read the findings list for anything that needs attention, such as an extension mismatch or a browser that could not load the file. Use the JSON button to save the report and Clear media to start over.
When this tool is useful
- A support agent triaging a 'video will not play' ticket who needs to know whether the container matches the .mp4 extension.
- A publishing coordinator checking duration and 1920 by 1080 dimensions before submitting a clip to an ad or streaming platform.
- A developer confirming that a renamed .mov upload is really QuickTime data before writing a server-side transcoding rule.
- A podcast producer estimating bitrate on a batch of exported episodes to catch one that was rendered at the wrong quality.
- A QA tester recording what a specific browser reports for a WebM file, since Safari and Chrome differ in codec support.
Practical tips
- A probe error usually means the browser lacks support for that container or codec, not that the file is broken; try another browser before assuming corruption.
- Whole-file bitrate includes audio, subtitles, and container overhead, so it will read higher than the video stream bitrate shown in an encoder.
- Signature detection only needs the first bytes, so a truncated download can still classify correctly and then fail the metadata probe.
- Audio files report duration but no dimensions, and the aspect ratio row shows Unavailable, which is expected rather than a finding.
- Keep filenames under 1,024 UTF-8 bytes and files above zero bytes; anything else is rejected before inspection begins.
Examples you can test
Load an example, compare the result with the expected output, then replace it with your own input.
MP4 with a matching extension
Example input
clip.mp4, 18,000,000 bytes, exported at 1920x1080 for 30 seconds
Expected output
Detected container MP4, MIME comparison match, duration 30.0 s, dimensions 1920 by 1080, aspect ratio 16:9, whole-file bitrate about 4.8 Mbps
The bitrate is 18,000,000 bytes times 8 bits divided by 30 seconds, so it reflects the whole file rather than one stream.
Renamed WebM
Example input
trailer.mp4 whose bytes begin with a Matroska/WebM signature
Expected output
Detected container WebM, MIME comparison mismatch, a finding that the extension disagrees with the signature, then browser duration if WebM is supported
The mismatch does not mean the file is dangerous, only that the name is wrong; rename it or transcode before distribution.
Validation checklist
- Confirm the detected container, extension, and MIME comparison all point to the same format.
- Check duration against the source edit or export log, not just the probe.
- Treat the bitrate row as a whole-file estimate and label it that way in reports.
- Play the file fully in the target browser or device; loaded metadata is not playback.
- Save the JSON report alongside the ticket so findings can be compared after a re-encode.