Skip to main content
DevBench

How to convert a video file

  1. Drop a video — MP4, WebM, MOV, AVI or MKV are supported (MTS/M2TS too) — or browse to it. A player preview confirms you picked the right clip.
  2. Choose the output: MP4 (H.264 video + AAC audio, with faststart so it streams while downloading) or WebM (VP9 + Opus).
  3. Set quality on the CRF slider (18–35): labelled High, Medium or Low — lower CRF is better quality and a bigger file; 23 is the balanced default.
  4. Press Convert and watch the progress bar; download when it finishes.

Where the encoding happens

FFmpeg — the industry-standard converter — runs here compiled to WebAssembly, inside your tab. The engine is about 25MB and is fetched once from a public CDN (jsDelivr) on first use, then cached by your browser; the status line says so rather than leaving you wondering. Crucially, your video file itself is never uploaded anywhere: it is handed straight to the in-page engine and the result is downloaded from memory. That makes it safe for unreleased footage and internal recordings, and it works with no account on any machine with a modern browser.

Practical limits

Encoding in the browser costs memory and time in proportion to clip length and resolution — keep the tab open while the progress bar runs, and expect a phone-sized minute-long clip to take roughly that long to re-encode. MOV and MKV containers convert cleanly because FFmpeg rewrites the streams regardless of the wrapper. When the goal is a shareable still or a looping clip rather than a video file, the GIF Maker tab on the same tool handles short segments.

Also useful: GIF Maker, Image Format Converter, and MIME Type Lookup.