Compress videos

What decides the size of a video

Every video file is a container (MP4, MOV, MKV, AVI) holding a compressed video track and usually an audio track. Its size is simply the bitrate multiplied by the duration:

Three things let an encoder use fewer bits without the picture falling apart:

• Resolution. 1080p has 2.07 million pixels per frame, 720p 0.92 million and 480p (854 × 480) about 0.41 million. Fewer pixels means each one gets more of the bitrate.
• Frame rate. Going from 60 to 30 frames per second halves the number of pictures to encode; for talking heads, lessons and screen recordings, 24–30 is enough.
• Codec efficiency. H.264 is the universal choice; VP9 and AV1 need fewer bits for the same quality but encode more slowly and play in fewer places.

How the video compressor works

The tool decodes and re-encodes the video inside your browser with WebCodecs, which uses the hardware video encoder of your computer or phone where available. The default output is an MP4 with H.264 video and AAC audio, which plays on practically every device and is accepted by every platform; WebM (VP9 and Opus) is available for websites.

You control the result in one of two ways. Enter a target size in megabytes and the tool calculates the bitrate from the duration, or choose a quality preset: High quality keeps nearly all visible detail, Balanced (the default) suits most sharing, Smallest file goes as far as is still watchable. On top of that you can limit the resolution (1080p by default, from 2160p down to 360p, measured on the shorter side), cap the frame rate at 60, 30 or 24, remove the audio track, set the audio bitrate and remove metadata. Very small targets lower the resolution automatically.

Honest limits of video in the browser

Video is the most demanding thing a browser tab can do, and it is fair to know the limits before you start:

• Browser support. WebCodecs is available in current Chrome, Edge and Opera, in Firefox 130 and later and in Safari 26 and later. Elsewhere the tool tells you so, and images, documents and WAV or AIFF audio still work.
• Speed. It depends on the hardware encoder. In our tests on a fast Windows PC, a minute of 1080p took Chrome about 20 seconds and Firefox about 48; an old phone can take far longer. Keep the tab open until the progress bar finishes.
• File size and memory. Very long or 4K recordings can exceed the memory a tab may use, especially on phones. The tool accepts up to 4 GB on a computer and 1 GB on a phone and rejects larger files with a message instead of crashing.
• Codecs. Browsers decode H.264, VP8, VP9 and AV1 well, and HEVC only on some devices. AVI, WMV, FLV and MPG files cannot be opened at all, and old codecs inside some MKV files may not be readable.

For a whole film collection, a desktop program such as HandBrake is the better tool.

Tips for better results

• Compress from the original recording. A video that has already been through a messenger has lost detail that cannot be recovered.
• Trim before compressing if you only need part of the clip; seconds you remove cost nothing.
• Screen recordings with small text need more bitrate than camera footage at the same resolution. Use Balanced or High quality, not Smallest file.
• If the result is slightly above your limit, run it again with a target 10 % lower; encoders cannot hit a size exactly.

Video compression questions