WebM vs MP4: which video format should you use?
WebM is the open web format; MP4 plays on everything. Quality, file size and compatibility compared, and which to use for websites, sharing, editing and uploads.
MP4 plays on everything; WebM plays in web browsers. WebM files are often a little smaller for the same quality, because they usually hold the more efficient VP9 or AV1 codecs. Use MP4 for anything you share, edit or upload, and WebM as a size-saving option on your own web pages — ideally alongside an MP4 fallback.
WebM vs MP4 at a glance
| WebM | MP4 | |
|---|---|---|
| Made by | Google, open and royalty-free | ISO standard |
| Typical video inside | VP8, VP9, AV1 | H.264, HEVC, AV1 |
| Typical audio inside | Opus, Vorbis | AAC, MP3 |
| File size at the same quality | Often smaller (VP9/AV1 vs H.264) | Baseline with H.264 |
| Chrome, Edge, Firefox | Yes | Yes |
| Safari | On web pages | Yes |
| iPhone Photos, many TVs and car screens | No | Yes |
| Editors (Premiere, iMovie, CapCut) | Often not | Yes |
| Upload forms | Often rejected | Accepted |
As with MOV vs MP4, the format is a container. What decides size and quality is the codec inside it — and WebM’s are newer than H.264, the codec most MP4s use.
Why WebM files are often smaller
VP9 and AV1, the codecs in most modern WebM files, compress better than H.264: VP9 is in the same class as HEVC, and AV1 is better still. So a WebM can hold the same picture in fewer megabytes, which matters for a web page where every visitor downloads the video. The flip side is encoding time — VP9 and especially AV1 are slower to encode than H.264.
Not every WebM is efficient, though. Many screen recorders produce VP8 at a high bitrate, which is neither small nor widely playable.
When to use WebM
-
Background and hero videos on your own website, where smaller files mean faster pages. Offer an MP4 fallback:
<video autoplay muted loop playsinline> <source src="hero.webm" type="video/webm"> <source src="hero.mp4" type="video/mp4"> </video> -
Web apps and browser-based tools, where the browser is the only player that matters.
When to use MP4
- Sending a video to anyone — especially iPhone users, whose Photos app will not import WebM.
- Editing — many editors ask for MP4 or MOV.
- Uploading to a form, course platform, or social network.
- Playing on a TV, car screen or games console.
- A web page with only one source — MP4 with H.264 plays in every browser.
Converting a WebM recording to MP4
Screen recordings, browser extensions and meeting tools often save WebM because that is what browsers record. To send one to someone or open it in an editor, convert it to MP4. VP8 and VP9 video is re-encoded to H.264 and Opus audio to AAC; WebM files that already hold H.264 — some Chrome recordings do — are copied across with no quality loss. It all runs in your browser, so the recording is never uploaded:
WebM to MP4Convert WebM recordings to MP4 that plays on iPhone, Windows and every editor. Batch convert several at once.Convert WebM to MP4So which should you use?
- Sharing, editing, uploading, TVs, iPhones: MP4.
- Video on your own web page: WebM first, MP4 fallback.
- Got a WebM that will not open: convert it to MP4.
Tools used in this guide
Free, and they run in your browser — nothing is uploaded. See every tool on the Video Tools page.
Frequently asked questions
Is WebM better quality than MP4?
Not inherently. Quality depends on the codec and bitrate inside. WebM usually holds VP9 or AV1 and MP4 usually holds H.264; VP9 and AV1 are more efficient, so at the same file size a WebM can look slightly better. At the same quality, the WebM is smaller.
Is WebM smaller than MP4?
Usually, when the WebM uses VP9 or AV1 and the MP4 uses H.264 — those codecs need less data for the same picture. An MP4 holding HEVC or AV1 can be just as small.
Can an iPhone play WebM?
Only partly. Safari can play WebM on web pages, but the Photos app will not import it and many iPhone apps cannot open it. To send a WebM to an iPhone user, convert it to MP4.
Should I use WebM or MP4 on my website?
Use both if you can: a WebM source first for smaller downloads in browsers that support it, and an MP4 fallback. If you only provide one, MP4 with H.264 plays in every browser.
Why are my screen recordings WebM?
Browsers record with the MediaRecorder API, and Chrome, Edge and Firefox save WebM by default. That is why browser-based screen recorders, extensions and meeting tools often produce WebM files.