Convert Always

Runs on your device

MP4 to WebM converter

This page converts MP4 to WebM without installing anything. Everything below explains what changes between the two formats so you know what to expect from the output.

Drop files here

Up to 20 files, 100.0 MB each. Conversion happens on your device — nothing is uploaded.

What is MP4?

MP4 is the universal video container, almost always carrying H.264 video with AAC audio. If a device plays video at all, it plays MP4.

Standardised by MPEG in 2001, based on Apple's QuickTime container.

  • The most compatible video format in existence
  • Hardware-accelerated decoding on virtually every chip
  • Streams progressively, so playback starts before the download finishes

What is WebM?

WebM is an open, royalty-free video container built for the web, pairing VP8/VP9/AV1 video with Vorbis or Opus audio.

Launched by Google in 2010.

  • Royalty-free, with no codec licensing to worry about
  • VP9 and AV1 beat H.264 substantially on file size
  • First-class support for transparent video and HTML5 playback

Why convert MP4 to WebM?

  • WebM is the better fit for self-hosted web video and background loops, while MP4 is built for sharing, uploading and playing video anywhere.
  • It sidesteps the main drawback of MP4: h.264 is less efficient than modern AV1 or HEVC.
  • You gain royalty-free, with no codec licensing to worry about.
  • Compatibility improves where it counts: Chrome, Firefox, Edge, Android and Safari 14+ for VP9, partially.

Quality and file size after conversion

Both formats are lossy, so this is a re-encode rather than a copy. Quality is set by the target bitrate or quality level rather than by the source, and each additional round trip costs a little fidelity. Convert once, from the highest-quality file you have.

Compatibility

MP4 opens in Every browser, phone, smart TV, console and editor. WebM opens in Chrome, Firefox, Edge, Android, Safari 14+ for VP9, partially.

If the file has to work for someone else, choose the format their software already understands rather than the one with the best specification.

Limitations to know about

  • WebM is lossy — the conversion is one-way and re-editing the output repeatedly will degrade it.
  • Safari support is partial and older Apple devices struggle
  • Poor support in desktop editors and social uploaders

When to keep MP4 instead

MP4 is still the right choice for sharing, uploading and playing video anywhere. Keep the original alongside the converted copy whenever you might need to re-export at a different size or quality — conversion is quick, but recovering discarded detail is impossible.

How to convert MP4 to WebM

  1. 1

    Drag your MP4 file onto the drop zone above, or click to browse. Up to 20 files can be queued at once.

  2. 2

    WebM is already selected as the output format — change it in the dropdown if you need something else.

  3. 3

    Press Convert and watch the per-file progress bar.

  4. 4

    Download the WebM result, or grab everything as a single ZIP when you converted a batch.

Frequently asked questions

Is this MP4 to WebM converter free?

Yes. Every conversion on Convert Always is free, with no account, no watermark and no daily download cap. The site is funded by advertising rather than subscriptions.

Are my MP4 files uploaded to a server?

No. MP4 to WebM runs entirely inside your browser using WebAssembly, so the file never leaves your device. You can even disconnect from the internet after the page loads.

Will converting to WebM reduce the quality?

Both formats are lossy, so this is a re-encode rather than a copy. Quality is set by the target bitrate or quality level rather than by the source, and each additional round trip costs a little fidelity. Convert once, from the highest-quality file you have.

Can I convert several MP4 files at once?

Yes. Add up to 20 files to the queue, convert them in one pass and download the results individually or bundled into a single ZIP archive.

What is the maximum MP4 file size?

Files up to 100 MB each are accepted. Browser-side conversions are limited mainly by your device's memory, so very large video files convert faster on a desktop than on a phone.

Does it work on mobile?

Yes. The converter is built mobile-first and works in Safari and Chrome on phones and tablets. Heavy media conversions are slower on mobile hardware but still run locally.

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