Video File Info & Codec Inspector
Inspect technical metadata for any video or audio file — codec, resolution, bitrate, frame rate, audio channels, and container details. Reads the headers only, so even a multi-gigabyte file answers in a moment — and it never leaves your browser.
How to inspect video metadata
- Drop in a file or browse your device. Any video or audio container is accepted.
- Instant header scan — the tool inspects stream descriptors and codec headers locally using WebAssembly.
- Review the streams — inspect resolution, bit depth, color space, audio channels, and encoding parameters.
- Copy report to copy a structured text summary for troubleshooting, bug reports, or client delivery specs.
What each technical field means
Container vs codec
The container (MP4, MKV, MOV) is the wrapper. The codec (H.264, VP9, ProRes) is the compression inside it. A file can use the same codec in different containers.
Profile, level & FourCC
The FourCC / Codec ID (e.g. avc1, hev1, apch) tells software the exact byte signature. Profile and level specify decoder limits like maximum resolution, macroblocks, and bitrates.
Bit depth & bits/pixel
8-bit gives 16.7M colours; 10-bit gives 1.07B for HDR. Bits/(Pixel*Frame) measures compression density — higher values mean less compression artifacting.
Color range & primaries
Limited range (16–235) is standard for TV/broadcast; Full range (0–255) is PC/gaming standard. Primaries define color gamut (Rec.709 for HD, Rec.2020 for UHD/HDR).
Channel layout & delay
Audio channel layouts (Stereo, 5.1, 7.1) map streams to speaker positions. Delay measurements reveal audio-video sync offsets introduced during capture.
Fast start & frame rate modes
Fast start means the index sits at the front, so a web upload plays before it finishes downloading. CFR gives every frame the same duration; VFR footage from phones and screen recorders is what drifts out of sync in an editor.
Frequently asked questions
Is my video uploaded to a server to read its metadata?
No. Everything runs inside your browser via WebAssembly (mediainfo.js). The tool reads only the small header and footer sectors of your file directly from your disk without uploading a single byte.
Can I inspect very large video files (e.g. 10 GB or 50 GB)?
Yes. Because the inspector streams only the container headers rather than loading the entire file into memory, even multi-gigabyte files are analyzed almost instantly.
What video and audio formats are supported?
Virtually all common containers and codecs: MP4, MOV, MKV, WebM, AVI, WMV, FLV, TS, MXF, MP3, WAV, AAC, FLAC, OGG, Opus, M4A, and more.
How do I check if my video is Variable Frame Rate (VFR)?
Look under the Video section in the report: the Frame Rate field indicates whether the video is Constant Frame Rate (CFR) or Variable Frame Rate (VFR). VFR footage from phones or screen recorders often causes audio sync drift in editing software.
Why does my MP4 say fast start is off?
An MP4 keeps an index (the moov atom) that a player needs before it can start. When it sits at the end of the file, a browser has to download the whole thing before playback begins — which is why an upload can look broken until it finishes. The General section reports this as Fast start, so you can check a file before you publish it.
How do I copy the full technical specification?
Click the 'Copy report' button above the results. It formats all general, video, audio, and subtitle streams into a clean, shareable plain-text summary ready to paste into tickets, forums, or chat.
What is the difference between container format and video codec?
The container (like MP4 or MKV) is the packaging file format that holds video, audio, and subtitles together. The codec (like H.264, VP9, or ProRes) is the actual compression algorithm used to encode the video stream inside that package.