WebM is the open, royalty-free video format built for the web. Converting MP4 to WebM gives you smaller, fast-loading video for websites and HTML5 players with wide browser support.
Convert MP4 to WEBM – Free Online MP4 to WEBM Converter
Why convert MP4 to WEBM?
- Faster page loads with efficient VP9/AV1 compression.
- Royalty-free format ideal for open-source and web projects.
- Native HTML5 <video> playback without proprietary codecs.
Tip: Keep an MP4 fallback alongside WebM for older Safari versions and maximum compatibility.
What is the difference between MP4 and WEBM?
| MP4 | WEBM | |
|---|---|---|
| Container origin | ISO/MPEG standard, the general-purpose default since the 2000s | Google-led open project purpose-built for HTML5 video |
| Typical codecs inside | H.264/H.265 video with AAC audio | VP8/VP9/AV1 video with Opus or Vorbis audio |
| Licensing | Codec patents licensed by device and software vendors | Royalty-free end to end |
| Encoding speed | H.264 encodes quickly with wide hardware help | VP9/AV1 encoding is markedly slower and CPU-heavy |
| Best for | Universal playback and a safe master copy | Web embeds where bandwidth and open licensing matter |
Does converting MP4 to WEBM lose quality?
This direction is always a full transcode — H.264 and AAC are excluded from WebM by specification, so both streams are rebuilt from scratch. Resolution and frame rate are carried over exactly, and at web-typical bitrates the newer codec represents the picture at least as faithfully as the source did, so visible degradation is unusual on a single pass.
The size result depends on how the MP4 was made. Camera footage and editor exports with generous bitrates usually shrink noticeably as WebM, which is the whole appeal for page-speed work. An MP4 that was already aggressively compressed for streaming has little fat left, and the WebM may land near the same size — the source's efficiency sets the floor.
Audio moves from AAC to Opus, which is an upgrade in efficiency terms: Opus holds transparent quality at lower bitrates than AAC. Speech-heavy content (tutorials, talking-head video) benefits most, with the audio share of the file often dropping by a third or more.
What can go wrong converting MP4 to WEBM?
- The conversion takes much longer than my other video conversions — VP9-class encoding is several times slower than H.264 by nature — that's the cost of its compression. Long or high-resolution files simply need more processing time; the upload itself isn't stuck.
- The WebM barely saved any space over my MP4 — Your MP4 was likely already tightly compressed, leaving little headroom. The gains show up on high-bitrate camera or export files, not on video that has already been optimized once.
- The video won't play on an older iPhone or iPad — Safari only gained WebM support in recent iOS/macOS versions, and older Apple devices never got it. Serve both files with two source tags in your video element and the browser picks what it can play.
- My source video is over the 50 MB free limit — Trim the MP4 to the segment you actually need, or export it at a lower bitrate first. Files under 50 MB convert free with no signup, and everything uploaded is deleted after an hour.
How to convert MP4 to WEBM
- Upload your MP4 file using the area above.
- WEBM is preselected as the target format.
- Click Start and wait for the conversion to finish.
- Download your converted WEBM file.