Add your MP4 file
Drop one or more .mp4 files onto the converter above, or browse for them. They load into browser memory only — nothing is uploaded, so there is no size-based pricing and no server queue.
MP4 to WEBM
Converting .mp4 video to .webm means re-encoding the picture and sound into a different container and codec family, and this page does it entirely in your browser. Free, private, and validated — the file never leaves your browser.
Private for supported formats — processed in your browser
Runs on your deviceConvert supported files
Drop MP4 files here
Batch files can each use a different output. Nothing uploads for local conversions.
Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.About converting MP4 video to WebM video
Converting .mp4 video to .webm means re-encoding the picture and sound into a different container and codec family, and this page does it entirely in your browser. An .mp4 file is a multimedia container that bundles compressed video, audio, subtitles, and chapter data into a single stream-friendly package. It is the default delivery format for nearly every phone, camera, and video platform, which makes .mp4 the safest target when a clip has to play everywhere.
A .webm file is an open, royalty-free video container built specifically for the web. It restricts itself to free codecs, VP8, VP9, or AV1 for video with Vorbis or Opus for audio, so any browser can play a .webm without patent licensing concerns. For this route the practical draw is free of patent royalties end to end and vP9 and AV1 deliver excellent compression efficiency — balanced against older iPhones and legacy Safari versions cannot play it, which is worth knowing before you commit a large batch.
Why convert MP4 to WEBM?
WebM exists for exactly one audience — the open web — and that is where this conversion earns its keep. VP9 video in WebM typically undercuts H.264 MP4 file sizes at comparable quality, the format is royalty-free (no codec licensing questions for your project), and every modern browser plays it natively in a <video> tag. If you are embedding clips on a site you control and care about bandwidth, converting your MP4 masters to WebM is one of the cheapest wins available.
MP4 vs WEBM at a glance
| Aspect | MP4 video (.mp4) | WebM video (.webm) |
|---|---|---|
| Format type | Container — quality depends on the codecs and settings inside | Container — quality depends on the codecs and settings inside |
| How it stores data | typically carries H.264/AVC or H.265/HEVC video with AAC audio, though the box structure also accepts AV1, MP3, and timed-text tracks | structured as a deliberately restricted subset of Matroska's EBML layout |
| Strongest at | publishing video to the web, social media, or a client who has not specified a format | serving HTML5 video without codec license fees |
| Weak spot | fewer track, attachment, and chapter features than Matroska | older iPhones and legacy Safari versions cannot play it |
| Metadata | iTunes-style metadata atoms (title, artist, cover art) plus XMP and per-track language tags; ID3 is not native to the container | only a minimal set of Matroska tags such as title and language is defined for WebM; the spec deliberately omits attachments and rich tagging |
Pick WEBM as the output
Select .webm in the output menu next to each file. The menu only offers targets this engine can genuinely produce, so if WEBM is selectable, the route is real and validated.
Convert on your device
Press Convert. The conversion runs on an FFmpeg engine compiled to WebAssembly, executing entirely inside your browser tab.
Verify and download
Each result is signature-checked before the download unlocks, so a failed encode can never masquerade as a valid WEBM file. Outputs keep the original filename with the .webm extension.
MP4 to WEBM questions, answered
Will converting MP4 to WEBM lose quality?
Both sides are re-encoded, so expect a small generation loss controlled by the quality setting: mp4 is container-oriented and webm is container-oriented. For visually or audibly transparent results keep quality high; for smaller files lower it and compare.
Is it private to convert MP4 files here?
Yes — the .mp4 file is processed inside your browser tab and never uploaded. The conversion runs on an FFmpeg engine compiled to WebAssembly, executing entirely inside your browser tab. Close the tab and the file is gone from memory.
Where will the WEBM file work?
Chrome, Firefox, and Edge have played WebM for over a decade, and Safari added playback in 2021 starting with version 14.1 on macOS, with iOS following in iOS 15. Beyond browsers the picture thins out quickly, since many televisions, set-top boxes, and editors still expect MP4.
Will the WEBM file be bigger or smaller than my MP4?
It depends on the content: structured as a deliberately restricted subset of Matroska's EBML layout. Convert one representative file first and compare before batch-processing a large set.
What happens to the metadata in my MP4 file?
This converter strips container metadata deliberately (the FFmpeg command runs with metadata mapping disabled) so exported files do not leak recording details. In the source, iTunes-style metadata atoms (title, artist, cover art) plus XMP and per-track language tags; ID3 is not native to the container; none of it is transmitted anywhere because the file never leaves your browser.
Can I convert WEBM back to MP4?
Yes — the reverse route exists as a separate tool. Bear in mind that round-tripping .mp4 → .webm → .mp4 is not a perfect undo when any lossy step is involved; keep your original if fidelity matters.