MP4 to WebM Converter
Make a WebM copy of an MP4 for your own website, a background loop or a platform that accepts only open formats. Audio is encoded as Opus, and the quality value starts where Google's own guidance for web video sits.
Video Converter
or drop MP4, MOV, MKV … files here ·
Max 95 MB per file· Up to 20 files· Deleted after 30 minutes
Files are processed on our servers and deleted after 30 minutes.
Lower is better quality and a bigger file. 18 looks identical to the source, 23 is the default, 28 and above shows visible softening.
Frames per second. Keep the source rate unless a platform asks for a specific one; 15–20 fps is plenty for GIFs.
Only used for PowerPoint files and single still images: how long each slide or picture stays on screen.
Auto uses AAC for MP4/MOV and Opus for WebM. Copy keeps the original sound untouched when the new format supports it.
192 kbps is transparent for music; 128 kbps is enough for speech.
Width of the animation in pixels; height follows the aspect ratio. 480 px suits chats, 720 px or more gives a high-quality GIF but a much larger file.
GIF holds at most 256 colors. Fewer colors make a smaller file but cause banding on gradients and skin tones.
Mixes palette colors in a fine pattern to hide banding. Sierra gives the smoothest result; none gives the smallest file.
Whether the animation repeats endlessly or plays one time and stops.
Optional. Seconds (e.g. 75) or minutes:seconds (1:15). Leave empty to start at the beginning.
Optional. Same format as the start time. Leave empty to keep everything up to the end.
The converted file will be at or just under this size.
How to use this tool
- 1
Upload the MP4s
Up to 20 files per batch, 95 MB each.
- 2
Set quality and audio
Quality (CRF) starts at 31 and Audio codec at Opus. Tick Remove audio for a silent background loop, or use Start at and End at to cut it to length.
- 3
Convert to WebM
Press Convert to WebM and download. Uploaded and converted files are deleted 30 minutes after processing.
How do I convert MP4 to WebM for a web page?
Upload the MP4, keep Quality (CRF) at 31 and Opus audio, press Convert to WebM, then list the WebM before the MP4 in your video tag so each browser picks the file it plays best.
Who needs WebM instead of MP4
Almost nobody needs WebM to watch a video. It is the publisher's format. Google created it in 2010 so HTML5 video could work without patent licensing, and it remains the format that Chrome, Firefox and Edge decode most efficiently. Hero videos, product loops and documentation clips on a site you control are the main reason to convert: a smaller file means a faster Largest Contentful Paint and less bandwidth on every visit.
The second group is open platforms. Wikimedia Commons accepts video only in free formats, so a clip for a Wikipedia article has to be WebM or Ogg. Telegram's animated video stickers are WebM by definition. Some game engines and browser-based tools also expect WebM for in-page playback.
If you are moving the other way, because a recording from your browser will not open in an editor, WebM to MP4 is the page for that.
Upload the MP4
H.264 or HEVC, up to 95 MB.
Re-encode for the web
WebM video at the CRF you set, Opus audio or none.
Embed with a fallback
WebM first, MP4 second in the video tag.
MP4
MPEG-4 video
MP4 (MPEG-4 Part 14) is a multimedia container standardised by ISO/MPEG and based on Apple's QuickTime format. It usually holds H.264 or HEVC video with AAC audio, and can also carry subtitles, chapters and metadata. It is the most compatible video format in the world, playing on phones, browsers, TVs, game consoles and social platforms. The video inside is almost always lossy, so repeated re-encoding gradually reduces quality.
- Compression
- Lossy
- Transparency
- –
- Animation
- –
- Introduced
- 2001 · Moving Picture Experts Group (MPEG)
WEBM
WebM video
WebM is an open, royalty-free video format released by Google in 2010 for the web. It is based on Matroska and holds VP8, VP9 or AV1 video with Vorbis or Opus audio, and VP9 WebM can include an alpha channel for transparent video. Browsers play it natively, and browser screen recorders often produce it. Apple devices, video editors and social platforms have historically had weaker support than for MP4.
- Compression
- Lossy
- Transparency
- Yes
- Animation
- –
- Introduced
- 2010 · Google
MP4 to WebM is a publishing conversion: site owners and open projects want a royalty-free, compact file for browsers, not a file that opens in more desktop apps.
Platforms that ask for WebM
| Organisation | Requirement | Source |
|---|---|---|
| Wikimedia Commons | Video in free formats only: WebM or Ogg. MP4 uploads are refused. | Commons:Video |
| Telegram video stickers | WebM with VP9, no audio, up to 3 seconds, 512 px on the longest side, 256 KB at most. | Telegram stickers |
| Your own site (HTML5 video) | WebM as the first source, MP4 as the fallback for browsers without VP9. | — |
Settings for a background video loop
A muted autoplay loop behind a headline has different needs from a tutorial. Tick Remove audio; browsers only autoplay muted video anyway, and an empty audio track still costs bytes. Set Resolution to 720p, because the loop usually sits behind text or a dark overlay, and raise Quality (CRF) to 36 or so. Trim it to the few seconds that loop cleanly with Start at and End at, then check the result loops without a visible jump.
For a short silent clip that will be shared rather than embedded, an animated image may serve better; MP4 to WebP makes one that loops on its own. When a WebM has to meet a hard cap, such as Telegram's 256 KB, turn on Limit file size and enter the number in KB.
MP4 to WebM converter FAQ
Is WebM smaller than MP4?
At equal visual quality, a VP9 WebM is usually noticeably smaller than an H.264 MP4, which is why sites serve it to browsers that support it. Compared with an HEVC MP4 the sizes are close.
Should I replace MP4 with WebM on my website?
Add it, do not replace. Put the WebM as the first <source> inside the video tag and the MP4 second; browsers take the first one they can play. Older Safari versions and some embedded browsers still need the MP4.
What CRF should I use to convert MP4 to WebM?
Google's VP9 guidance for on-demand video suggests a CRF around 31 for 1080p, which is this page's default. Go lower, toward 24, for detailed footage you want crisp, or higher for a soft background loop where size matters more.
Can I make a WebM with a transparent background from an MP4?
No. H.264 MP4 has no alpha channel, so there is no transparency to carry over. Transparent WebMs have to be rendered from a source that has alpha, such as an animation exported from After Effects or Blender.
Why does my WebM not play on an older iPhone?
Apple added WebM playback to Safari later than other browsers, starting on the Mac with Safari 14.1 in 2021. Older iOS devices and many in-app browsers skip it, which is why the MP4 fallback stays in your page.
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