Why it exists
Chat apps, email providers, forms and issue trackers all cap attachment size. Most online compressors make you upload your video to their server first, which is slow and not something everyone is comfortable with. shrinkto.app does the work on your own computer instead.
How it works
Modern browsers include hardware-accelerated video codecs. shrinkto.app uses them through the WebCodecs API to decode your video, re-encode it as H.264 video with AAC audio, and package it as an MP4 file. Your file is read from disk in pieces; it is never sent over the network.
- It first works out a bit budget for your target size and keeps about 3% in reserve for the container.
- It then chooses an audio setting and a video bitrate, lowering resolution or frame rate only when the quality would otherwise fall too low. It never upscales.
- After encoding it measures the real file. If the result is over your limit, it re-encodes with a corrected bitrate, up to two more times.
- The finished MP4 has its index at the start of the file so it starts playing quickly.
Images
For images, the browser decodes your picture and re-encodes it as JPEG or WebP. The tool searches for the highest quality that stays under your limit and only reduces the pixel dimensions if the quality alone cannot get there.
Browser support
Google Chrome and other Chromium-based browsers give the best and fastest results. Other browsers may switch to a slower compatibility mode based on ffmpeg compiled to WebAssembly.
Privacy
Your videos stay on your device. Read the full details in the privacy policy.
Contact
Questions, bug reports and suggestions are welcome at [email protected].