No upload, 100% local, no account

Video converter

Pick a target container and codec, then convert in your browser. Your file never leaves your device.

How Video converter works

Convert a video from one container and codec to another entirely inside your browser, with ffmpeg WebAssembly doing the work on your device. You choose the output container (MP4, WebM, MKV, or MOV) and the video codec (H.264 via libx264 or VP8 via libvpx). Only valid combinations are offered: WebM pairs with VP8 and Opus audio, MP4 and MOV use H.264 with AAC audio, and MKV can hold either.

Changing codec always means decoding every frame and re-encoding it from scratch, which is CPU-intensive. H.264 is the fast, plays-everywhere choice; VP8 sits in the same size and speed class and is here because WebM requires a VP codec. A 30-second clip converts in seconds; a 20-minute recording may take several minutes on a mid-range laptop. There are no watermarks and no account required.

Written by Bastien Sulyan

How to use Video converter, step by step

  1. Drop or select the video file to convert.
  2. Pick the output container format (MP4, WebM, MKV, or MOV).
  3. Select the video codec (H.264 or VP8) from the options available for that container.
  4. Quality is handled for you: the tool applies fixed, sensible defaults (CRF-based quality for VP8, a balanced preset for H.264) rather than exposing encoder knobs.
  5. Click Convert and wait while ffmpeg re-encodes the video on your device, then download the result.

Common use cases

  • Converting a MOV file from an iPhone to MP4 H.264 for compatibility with a video editor on Windows.
  • Producing a WebM version of a clip for a site that standardizes on the royalty-free WebM/VP8 stack.
  • Converting an AVI or older container to MKV H.264 so an old capture stays playable in modern players.
  • Creating an MP4 H.264 copy of a WebM recording for platforms that do not support WebM playback.

Frequently asked questions

Is my video uploaded anywhere during conversion?

No. ffmpeg.wasm runs libx264 or libvpx inside your browser tab. Your file is read into local memory, re-encoded there to the container and codec you selected, and the result is saved to your device. No frame of your video is sent over the network.

Which codec should I choose?

H.264 is the widest-compatibility choice and the fastest to encode: pick it unless you specifically need WebM. VP8 compresses about as well as H.264 and exists here as the WebM codec, for a fully royalty-free output. Newer codecs such as H.265, VP9 and AV1 do compress better, but their encoders do not run reliably in the browser's WebAssembly engine, so this tool does not offer them.

Why is conversion so much slower than trimming or muting?

Trimming in copy mode and muting skip the video re-encode entirely. Conversion must decode every compressed frame, process it, and re-encode it with the new codec. That is inherently many times more work than copying a stream, which is why duration and resolution drive the conversion time.

Can I convert a video to WebM for use on a website?

Yes. Select WebM as the container; the tool automatically pairs it with VP8 video and Opus audio. WebM is royalty-free and supported in Chrome, Firefox, Edge, and Safari. Providing both an MP4 H.264 and a WebM version lets you serve every browser from an open format.

Does the tool preserve subtitles or chapters when converting to MKV?

The converter focuses on video and audio streams. Soft-subtitle tracks or chapter markers from the source may not be carried through automatically. For subtitle preservation you would need to mux them in separately after conversion.

Does the converter work offline once the page has loaded?

Yes. The ffmpeg.wasm engine is downloaded on the first visit and is sizeable, but once loaded the full codec conversion runs on your device with no internet connection required. You can close the network connection after the page and engine finish loading.

Can I convert a video on my phone?

Yes for a short clip; a full re-encode is heavier on memory than a copy-mode operation, and a phone browser tab has much less RAM available than a desktop one. A minute-long clip converts fine on most recent phones. A long recording is safer to convert on a computer.