Video Compressor

Phone videos are recorded at high bitrates, so a one-minute clip can easily pass 100 MB — too big for e-mail, chat apps or upload forms. This compressor re-encodes the video as an H.264 + AAC MP4, which every phone, browser and TV plays, and lets you trade picture detail for size. It runs entirely in your browser with the ffmpeg video engine (about 30 MB, downloaded the first time), so nothing is uploaded.

How to use this tool

1. Choose one or more videos (MP4, MOV, MKV, WebM, AVI and others).
2. Pick a compression level — or "Target file size" and the size in MB you need.
3. Optionally cap the resolution (720p is plenty for phones) and the frame rate, or remove the sound.
4. Press Calculate and wait for the progress bar; then compare the sizes and download the result.

Formula

Target mode: video bitrate (kbps) = target bytes × 8 × 0.95 ÷ length (s) ÷ 1000 − audio bitrate

The 5% margin covers the MP4 container and encoder variation. In the quality levels, CRF (constant rate factor) keeps the picture quality steady and lets the size follow the content: every +6 CRF roughly halves the bitrate. Lowering the resolution from 1080p to 720p removes more than half the pixels, which is the biggest single saving.

Example

A 90-second clip must fit under a 25 MB e-mail attachment limit. Video bitrate = 25,000,000 × 8 × 0.95 ÷ 90 ÷ 1000 − 128 ≈ 2,111 − 128 = 1,983 kbps, which looks good at 1080p and very good at 720p. The result lands at about 23.5–24.5 MB.

How long it takes

The engine runs on one processor core inside the tab. On a recent computer it encodes about 25 frames per second at 480p, 12 at 720p and 6 at 1080p. Shrinking a 1080p phone video to 720p runs at about 8 frames per second, because every full-size frame still has to be decoded, so a one-minute 30 fps phone video takes roughly 4 minutes at 720p and 5 minutes at 1080p. Phones are slower and have less memory: keep clips short there and leave the tab open while it works.