Video compressor

Open a video and this tool encodes several smaller versions of it entirely in your browser, using FFmpeg compiled to WebAssembly. Nothing is uploaded anywhere. Versions are H.264 + AAC .mp4 files with settings chosen to play in as many mobile browsers and operating systems as possible, or silent, looping animated .webp images that work anywhere a GIF would. Compare them side by side and download the smallest one that still looks good.

Embed on a web page

Upload the video and the poster image alongside your page, then paste this in. It uses the first video shown in the results above. preload="none" means the browser only shows the poster image and does not download any of the video until someone presses play.

Upload the animated WebP alongside your page, then paste this in. It uses the first version shown in the results above. It plays automatically and loops, with no sound. loading="lazy" means the browser waits until the image is about to scroll into view before downloading it. Fill in the empty alt with a description of the clip.

XHTML

How the output files are made compatible:

H.264 video (libx264) in the Main profile by default, 8-bit 4:2:0 colour (yuv420p), even width and height, capped at 1080p and 60 fps. The H.264 level is picked automatically from the resolution and frame rate.
AAC-LC audio at 44.1 or 48 kHz, downmixed to stereo when the source has more channels.
MP4 container with the index moved to the front (+faststart) so playback can begin before the file has fully downloaded.
Only the first video and first audio track are kept. Rotation metadata from phones is baked into the pixels so every player shows the video the right way up.
Animated WebP versions use libwebp's animation encoder (libwebp_anim): lossy, 4:2:0 colour, set to loop forever, with no sound and no metadata. The frame rate is capped (15 fps by default) and never raised above the source's. They display as an ordinary <img> in every current browser, including Safari 14 and later, but are usually several times larger than the MP4 at the same resolution: WebP can only skip the parts of a frame that did not change, where H.264 also tracks movement.

Encoding runs on a single CPU core inside WebAssembly, so it is much slower than a native ffmpeg. Long or high resolution videos can take a while: use the "first N seconds" option to compare settings quickly, then encode the full version of the one you like. The ffmpeg engine (about 32 MB) is downloaded once and cached by your browser.

Video compressor

Versions to generate

Results, smallest first

Poster frame

Embed on a web page