Compress video by format

The same compressor runs on every page here — the difference is what it is set to and what the page explains. Start from the file you have, the limit you are hitting, or the place you are sending it. If none of those apply, the main compressor does the general case.

Start from the file you have

The container your video is in changes what is worth doing to it. An AVI full of MJPEG has enormous room to improve; a WebM encoded with VP9 has very little. These pages explain what to expect before you spend the encoding time.

Three kinds of problem, and only one needs a re-encode

Those pages sort fairly cleanly by what is actually wrong with the file, and working out which group you are in can save you the encode entirely.

  • The wrapper is the problem. MKV, MOV, M4V, MTS and a late FLV usually hold perfectly ordinary H.264, and something is simply refusing to open the container. Remux copies the video untouched into a new wrapper in seconds, loses nothing, and changes the file size not at all. This is the right answer far more often than people expect.
  • The codec is the problem. AVI, WMV and an early FLV hold something one or two generations behind H.264. Re-encoding buys efficiency rather than costing quality, so the reduction is usually large and mostly invisible. Remuxing will not help here: with AVI it is possible but pointless, because the wrapper is not what is making the file big, and WMV cannot be remuxed into MP4 at all — the muxer refuses VC-1 and WMA.
  • The bitrate is the problem. MP4, WebM, a phone recording, a camcorder dump. Nothing is wrong with the file, there is just more of it than you need. This is the only group where making it smaller genuinely costs you picture quality, and the only one where a size target is the right way to think about it.

Several formats appear in more than one group, which is honest rather than sloppy: it depends on the file. A MOV holding H.264 is a wrapper problem and a MOV holding ProRes is not. When you are unsure, try Remux first. It takes seconds and either produces a working file or fails immediately, and either outcome tells you which group you are in.

Start from a size limit

If something rejected your file with a number attached, this is the faster route. Each page opens the compressor with that ceiling preset and shows what fits inside it at every clip length.

The size-target hub compares all 10 against four clip lengths in one grid, and has a shorter path through them if you do not know which limit you are up against.

Start from where it is going

Platforms differ in more than their limits. Some re-encode whatever you send, which changes the right strategy entirely — you want to hand over the best quality that fits rather than the smallest file you can make.

Container versus codec, in one paragraph

The distinction underneath this whole page is worth having straight. The container — MP4, MOV, MKV, WebM, AVI — is the wrapper: it holds the streams and the timing that keeps them in step, and it decides whether a given player will open the file at all. The codec — H.264, HEVC, VP9, MJPEG — is what actually compresses the picture, and it decides how large the file is.

That is why "convert this MKV to MP4" and "make this file smaller" are different jobs with different costs. Changing the wrapper is nearly free and takes seconds; changing the picture means decoding and re-encoding every frame. The Remux mode does the first, and the compression modes do the second. The formats reference lists what plays where.

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