Compress Video
Upload a video and compress it using the H.264 codec with a configurable CRF (Constant Rate Factor) parameter. CRF controls the quality-vs-size tradeoff: lower values (18-23) preserve more detail at larger file sizes, while higher values (28-51) produce smaller files with more compression artifacts. The default of 28 is a good starting point for general sharing.
You can also optionally downscale the resolution to 720p or 480p for further size reduction — useful for videos destined for social media, messaging apps, or email where full resolution isn't needed.
Everything runs in your browser using ffmpeg.wasm — your video is never uploaded to a server. The first load takes a few seconds to download the WebAssembly runtime, but subsequent uses are instant.
By The Paper Room Editorial Team — Video Tools
Frequently asked questions
What is CRF and what value should I use?▼
CRF (Constant Rate Factor) controls the quality-vs-size tradeoff for H.264 encoding. Lower values mean higher quality and larger files; higher values mean more compression and smaller files. 18 is visually lossless, 23 is the ffmpeg default, 28 is good for general sharing, and 51 is maximum compression with visible quality loss. Start at 28 and adjust from there.
Does this upload my video to a server?▼
No. The entire compression happens in your browser using ffmpeg.wasm (a WebAssembly port of ffmpeg). Your video never leaves your device.
Why does the first load take a few seconds?▼
The first time you use any ffmpeg-based tool, your browser downloads the ffmpeg WebAssembly binary (~30 MB). This is cached after the first load, so subsequent uses start instantly.
What video formats are supported as input?▼
MP4, MOV, AVI, MKV, and WebM files are accepted. The output is always an MP4 file with H.264 video and AAC audio, which is universally compatible.