Guide
Your video never has to leave this device
Updated 2026-08-28 · 8 min read
Most “online compressors” mean “upload it to our servers, we encode it, you download a watermarked file.” Shrink Clip means the opposite: the encoder is a program that runs inside your browser tab. This article is the honest version of how that works, what it is good at, and where it struggles.
Upload tools vs on-device tools
An upload compressor is a website with a hard drive and a queue. You send the original across the internet. They store it at least long enough to encode. Some delete it; some do not. You cannot verify. For a meme, that may be fine. For a work recording, a child’s recital, or unreleased footage, it is a bad trade.
An on-device compressor downloads a public encoder (here, ffmpeg compiled to WebAssembly, about 30 MB, cached after the first run). Your file is read into memory in the tab. The CPU on your laptop or phone does the work. Close the tab and that copy is gone. We cannot watch a file we never received.
What ffmpeg.wasm is — and is not
ffmpeg is the same family of software used in countless desktop tools. The WebAssembly build is a real encoder, not a toy filter. It can two-pass H.264, extract MP3, make a GIF, crop to 9:16. It is slower than a native app with a GPU, and browsers cap memory. A 20 GB camera dump on a phone will fail. A 200 MB screen recording on a laptop usually will not.
The first run downloads the engine. After that it should load from cache. That download is the encoder binary, not your video. If a corporate network blocks the CDN, you will see a load error — not a privacy leak.
Why this is slower than a “magic 3-second” site
Those sites have racks of servers. You wait in their queue; they burn electricity you do not see. In the browser, you wait on your own CPU with the tab in the foreground. A 15-second clip may finish in a few seconds. A 10-minute 1080p file can take minutes. That is expected. Keep the tab visible so the browser does not throttle it.
Two-pass encoding does the clip twice on purpose. Pass one measures; pass two spends bits. It is the difference between landing under 25 MB cleanly and guessing.
What we still do not see
Shrink Clip shows ads and uses Google Analytics on page views. That is how a free tool stays online. Those systems see that someone loaded a URL. They do not receive the video file. There is no account, so there is no inbox of past clips. Read the privacy policy if you want the cookie detail.
If your threat model is “nobody on the internet should know I compressed a file,” use a desktop ffmpeg command and stay offline. If your threat model is “I do not want this footage sitting on a random encoder farm,” a browser encoder is the right shape of tool.
Ready to try it? Compress a video in your browser— nothing is uploaded.