Vis Exo
CONVERT — MP4 TO WEBM
MP4 to WebM Converter, Free and In Your Browser
WebM exists because the web needed a video format with no licensing strings attached. VP9 usually beats H.264 on size at the same quality, and Opus does the same for audio, which is why so much streaming video on the web is WebM underneath.
When WebM Beats MP4
Smaller for the same picture
VP9 stores the same visual quality in fewer bytes than H.264, and Opus is more efficient than AAC. For a clip that will be served from a web page, that is bandwidth saved on every single view.
Royalty-free, by design
WebM was built from open codecs — VP9, Opus and formerly Vorbis — with no licensing body to satisfy. For an open-source project or a public archive, that matters as much as the file size.
Plays everywhere except Apple
Chrome, Edge and Firefox play WebM natively, and a plain video tag needs no extra work. Safari and iOS do not, so keep the MP4 if the same clip has to work on an iPhone.
The picture can be good too
This is a real re-encode, not a container rename. Keeping the original resolution and choosing High quality gives VP9 enough bitrate to look clean.
Three Steps, In Your Browser
- 1
Choose the MP4
Drop it in and check the read-out; it names the source codecs, so you know exactly what is being re-encoded.
- 2
Set the target to WebM
Switch the target from MP4 to WebM. The page then plans VP9 video with Opus audio, and says so in plain language before you start.
- 3
Convert and save
VP9 encoding is slower than H.264, so allow more time than a container swap. Play the result back before downloading it.
MP4 to WebM on iPhone, Mac, Windows and Android
The same page works everywhere, with nothing to install. What differs is where the file comes from and where it goes.
iPhone & iPad
Recent Safari versions can encode VP9, so the conversion runs on the phone itself.
Mac
Chrome and Edge encode WebM fastest; the file is ready for any web page.
Windows
Chrome or Edge produce WebM that every current browser plays.
Android
Chrome on Android encodes VP9 natively, so WebM is quick to produce there.
WebM, or Leave It as MP4?
Three options, honestly compared — including when the right answer is to convert nothing at all.
| Target | Pick it when | Watch out for |
|---|---|---|
| WebM — VP9 + Opus | Web pages, and anything that benefits from a royalty-free container. | Slower to encode than H.264 and many editors still will not open it. |
| Keep the MP4 | Maximum compatibility, or handing the file to someone else to edit. | If it is already H.264 in MP4 there is nothing to gain here. |
| MP4 — H.264 + AAC | The source is HEVC, AV1 or VP9 in MP4 and something old needs to play it. | This is the fallback target, not the usual reason to open this page. |
MP4 to WebM FAQ
Is WebM better than MP4?
Not universally. WebM is smaller and licence-free, which makes it the better choice for serving video from a web page. MP4 is the better choice for files that have to open in other people applications, because Apple devices and most editing software do not read WebM.
Can I keep both?
That is the usual approach: a WebM for the video tag and an MP4 as the fallback source. Both can be produced from the same original here.
Why is the WebM conversion slower than the others?
VP9 is a more computationally expensive encoder than H.264, and this is a full re-encode rather than a container swap. Hardware acceleration helps where the browser offers it, but expect it to take longer.
Will the WebM play on my iPhone?
No. Safari and iOS do not support VP9 in WebM for general playback, which is exactly why the fallback MP4 matters for a page that iPhone visitors will open.
Does it keep my audio?
Yes, as Opus, which is the standard WebM audio codec and is supported by the same browsers that play the video.
Related Converters
WebM to MP4
Screen recordings and browser captures arrive as WebM, which iPhones and QuickTime will not open. This turns them into H.264 MP4s.
Compress a Video
Keep the format, drop the resolution and the bitrate — the same engine that converts also makes files smaller.
MOV to MP4
QuickTime files that already hold H.264 and AAC are re-wrapped rather than re-encoded — near-instant, with nothing lost.
HEVC to H.264
Modern phones record H.265 to save space, then half the world will not play it. This converts it to H.264, the codec everything decodes.
Convert it, then track something in it
Vis Exo adds blob tracking, pose skeletons, trails, LUT grades and captions to the finished MP4 — free, and entirely in your browser.