Convert any video to WebM

MP4, MOV, MKV, WMV, AVI — drop it in and get a WebM out. Runs entirely in your browser. Your files never leave your device.

100% browser-basedNo file size limitNo registration required
Your WebM will appear here

Why choose VidToWebM?

VidToWebM

  • Files never leave your device — true privacy
  • No upload bandwidth, no waiting in a queue
  • No signup, no email, no tracking pixel
  • Works offline after first load (PWA)
  • Free forever — no premium tier

Typical online converters

  • Upload your file to someone else's server
  • Hit hard size limits behind a paywall
  • Force account creation or email capture
  • Plaster the page with ads & trackers
  • Hold conversion behind a daily quota

How to convert video to WebM

Four steps. No upload, no signup.

1
Drop your video

Drag and drop, or click to choose any video file from your device.

2
Wait for the converter to load

FFmpeg loads once in your browser (~30 MB) — subsequent conversions are instant.

3
Conversion runs locally

Your file is decoded and re-encoded as WebM right in your tab. Nothing is uploaded.

4
Download the WebM

Preview the result, then download. The original file never leaves your device.

The simplest way to convert MP4, MOV, and MKV to WebM

WebM is the open-source video format that powers HTML5 video on the web. It produces smaller files than MP4 at comparable quality, plays natively in every modern browser, and embeds cleanly in places that don't accept MOV or MKV — from GitHub READMEs and Reddit comments to Discord, Slack, and Notion. If you have a video in MP4, MOV, MKV, WMV, or AVI and need a WebM, this tool does the job in your browser.

Why convert in the browser?

Most online video converters are server-side: you upload your file, wait in a queue, and trust the operator with your data. We do it differently. VidToWebM uses FFmpeg compiled to WebAssembly, so the entire conversion happens inside your browser tab. Nothing is uploaded. No one sees your video — not us, not a CDN, not an ad network. When you close the tab, the file is gone.

When to use a browser converter vs. a desktop tool

  • Use VidToWebM for one-off conversions, sensitive footage, or when you don't want to install anything.
  • Use desktop FFmpeg or Handbrake for batch conversions, multi-GB files, or when you need fine-grained encoder control.

Output details

VidToWebM outputs VP8 video + Opus audio in a WebM container — the most universally supported WebM codec combination. Output is capped at 720p by default to keep browser memory usage in check; smaller sources are passed through at native resolution. Bitrate defaults to 1 Mbps for video and 128 kbps for audio.

Frequently asked questions

Are my videos uploaded anywhere?

No. VidToWebM runs entirely in your browser using WebAssembly. Your video file is never sent to a server — it's read, converted, and downloaded locally on your device.

What input formats are supported?

MP4, MOV, MKV, WMV, AVI, M4V, FLV, 3GP, and more. If a format ships with FFmpeg, it should work here. The output is always WebM (VP8 video + Opus audio).

Is there a file size limit?

There's no hard limit imposed by us — but because conversion happens in your browser, very large files (multi-GB) may exhaust your tab's memory. For best results, stay under ~500 MB.

Why does my output look smaller than the original?

By default we cap output at 720p to keep encoding fast and memory-light in the browser. Smaller source videos are passed through at their original resolution.

Why WebM instead of MP4?

WebM is the open, royalty-free format used across the modern web. It's the standard for HTML5 video, supported by every major browser, and works great for embedding in pages, GitHub READMEs, and chat platforms.

Do I need to sign up?

No accounts, no email, no signup. Open the page, drop a video, download the WebM. That's the entire flow.

Does it work offline?

After the first load, yes. The converter is a Progressive Web App — once cached, it runs without an internet connection.

Why is conversion slow?

Browser-based video encoding is single-threaded and CPU-bound. We trade speed for the privacy of never uploading your file. For very large videos, a desktop tool like FFmpeg or Handbrake will be faster.