Video Metadata Viewer

What to check when an upload gets rejected

Platforms are usually vague about why a file failed. These are the causes worth ruling out first, roughly in order of how often they are the answer.

• No audio stream. Several platforms, Amazon among them, reject silent files outright. This is the most common surprise, because the video plays fine locally.
• An unusual codec. H.264 in an MP4 container is accepted everywhere. HEVC, VP9, ProRes and AV1 are accepted in fewer places than their popularity suggests.
• A frame rate outside the expected range. Very high frame rates, and variable frame rate from screen recordings, cause more rejections than they should.
• A pixel format other than yuv420p. yuv422p and yuv444p are valid and widely unsupported. This one is invisible until you look.
• Resolution or aspect ratio outside what the placement allows.

Reading a bitrate

Bitrate is bits per second of video, and it is the number that explains file size: size ≈ bitrate × duration. It is also the number that explains quality, because a frame can only be as detailed as its share of the budget.

Rough expectations for H.264: around 2–5 Mbps for 1080p, 1–2.5 Mbps for 720p, and under 1 Mbps for 480p. Substantially below those and the footage will show it; substantially above and you are carrying file size for detail the viewer will not see on a phone.

If a file is unexpectedly large, the bitrate is where to look before anything else.

Why it reads the file in two stages

Your browser already knows the duration and the dimensions — it has to, in order to play anything — so those appear the moment you pick a file.

Codecs, frame rate and bitrate live inside the container and need a decoder to read. That decoder is a 30 MB WebAssembly download on first use, which is too much to spend on someone who only wanted to know how long a clip was. So it is a second, optional step.

Why this one does not upload your file

Inspecting a file should not require giving a copy of it to anyone. That is doubly true here, since the files people inspect are usually the ones that are not working yet — unreleased cuts, client work, things not meant to be seen.

The decoder is compiled to WebAssembly and runs in this tab. Nothing is sent anywhere.

Frequently Asked Questions

Is my video uploaded anywhere?

No. The decoder runs in your browser through WebAssembly. You can disconnect from the internet after the page and decoder have loaded and it still works.

Do I need an account?

No. No sign-up, no email, no watermark.

Why does it say no audio stream?

Because the file genuinely has none. Screen recordings made without system audio and silently exported clips are the usual causes. Several platforms reject silent video, which is often why an upload failed.

What codec should I be using?

H.264 in an MP4 container, with yuv420p pixel format and AAC audio. That combination is accepted essentially everywhere. HEVC and AV1 are more efficient and accepted in far fewer places.

What is a pixel format and why does it matter?

It describes how colour is stored. yuv420p is the near-universal choice; yuv422p and yuv444p keep more colour detail and are rejected by a lot of players and platforms. If a file will not play anywhere but your editor, this is a good thing to check.

Is my bitrate too low?

As a rough guide for H.264: 2-5 Mbps for 1080p, 1-2.5 Mbps for 720p. Below that, compression artefacts become visible in motion. Above it, you are mostly adding file size.

Why do I have to click a second button?

Duration and dimensions come from your browser instantly. Codecs and bitrate need a 30 MB decoder, and downloading that for someone who only wanted the duration would be rude.

Which formats can it read?

Most things ffmpeg can open, which is nearly everything — MP4, WebM, MOV, AVI, MKV and more.