How to prove a compressor doesn’t upload

Updated 11 Sep 2026 · shrinkclip.app

Many “free online compressors” upload your file to a server. You can verify that in about thirty seconds.

Protocol

  1. Open Chrome or Edge DevTools (F12) → Network tab.
  2. Optional: check Disable cache and click the clear button.
  3. Filter by Fetch/XHR or view All.
  4. Drop a video on the compressor and start encoding.
  5. Watch for a large POST/PUT of your media. If the only sizable downloads are the encoder (WASM / worker, often tens of MB once), and your video never appears as an upload, processing is local.

On shrinkclip.app, the video is read in-tab with ffmpeg.wasm. Ads and Analytics may still load (page-level) — that is not the same as uploading your footage. Details in the privacy policy.

This page is for readers and journalists who want a reproducible check — not a claim that every third-party tool is safe.