Rescreen / Free tools / MP4 to WebM

MP4 to WebM converter

Drop an MP4 here for a WebM with VP9 and Opus, re-encoded in your browser with little visible loss.

Drop an MP4 file here

or choose one from your device

Up to 2.0 GB. Stays on your device.

How to convert MP4 to WebM

Three steps, all on this page.

Choose your MP4
Choose or drop an MP4 file. The page reads what is inside and checks that this browser can convert it before anything starts.
Convert to WebM
Pick the options you want, then press Convert to WebM. Tracks that a WebM can hold as they are get copied, which is near instant.
Check and download
The new file is opened again and checked against the original before it is offered. Play it in the preview, then download it.

What changes from MP4 to WebM

WebM is based on Matroska and was made for the web. Every WebM player must handle VP8 and VP9 video and Vorbis and Opus sound; AV1 video is allowed too. Source
VP9 is open and royalty-free. It gives better quality than H.264 at the same bitrate, and about the same as HEVC. Source
VP9 plays in all current Chrome, Edge, Firefox, Opera and Safari. Safari does not show a VP9 video’s transparency. Source
An MP4 with H.264 and AAC plays in every major browser. When a site can offer only one video format, MDN’s advice is to make it MP4. Source
Opus is an open audio codec that handles speech and music alike, at anything from 6 to 510 kbps. Source
Google’s VP9 settings for video on demand aim at about 1,800 kbps for 1080p and 1,024 kbps for 720p at 30 frames a second. Source
HandBrake writes WebM with VP8, VP9 or AV1 video and Vorbis or Opus sound. Source

MP4 file

MP4 (ISO base media)

PictureH.264 or HEVC
SoundAAC

WebM file

WebM

PictureVP9
SoundOpus

Who converts MP4 to WebM

Mostly web developers: someone embedding a clip in a page who wants an open, royalty-free format, or a <video> element that offers WebM first and MP4 as the fallback. Also people whose upload form, ad spec, course platform or game engine asks for WebM by name, and people who were told WebM is smaller and want to see whether it is for their file.

What happens to the picture and sound

Both are re-encoded. An MP4 almost always holds H.264 video and AAC sound, and a WebM can hold neither, so unlike MOV to MP4 there is nothing to copy across. The picture becomes VP9 and the sound becomes Opus. VP9 is the safe choice for WebM: every current browser plays it, and every browser we tested could encode it, Safari included. AV1 makes smaller files but is far slower to encode, which matters when the encoding happens on your own computer.

Re-encoding always loses a little, the way saving a JPEG again does. The converter picks a VP9 bitrate from the original’s, so a sharp MP4 stays sharp; the loss is usually invisible at normal size but shows first in fine text and fast motion. If your MP4 is one of the rare ones that already holds VP9 or AV1 with Opus, those are copied without re-encoding and the page says so.

How big the WebM is, and how long it takes

We converted two one-minute MP4s on this page: a 1080p screen recording made with Rescreen, and 720p webcam footage recorded in Chrome. The webcam clip came out about a third smaller. The screen recording came out more than three times bigger, because it was already tiny: the original picture used only about 220 kbps, and the converter will not go below roughly 1,100 kbps at 1080p, a floor set so small text stays readable.

How long it takes depends more on the browser than on the file. Chrome and Safari finished each minute of video in about six seconds, ten times faster than it plays. Firefox’s VP9 encoder took over a minute for the webcam clip and two minutes for the 1080p one, so expect about twice the video’s length there. For a long video, use Chrome, Edge or Safari, and keep the tab in front while it runs.

MP4	Size	Chrome	Safari	Firefox
Screen recording, 1920×1080, 30 fps	2.5 MB	8.5 MB in 6 s	8.4 MB in 7 s	4.2 MB in 2:02
Webcam, 1280×720, 30 fps	22.4 MB	14.6 MB in 6 s	15.6 MB in 6 s	10.4 MB in 1:16

Two one-minute H.264 MP4s converted to WebM on this page at the default quality, on an M1 Mac (macOS 15.8), with the time each took (minutes:seconds where over a minute). Chrome 155, Firefox 157, and Safari’s engine as Playwright builds it (WebKit 27.2).

Smaller, Balanced or Best

The Quality menu moves the VP9 bitrate up or down from the one the original suggests. On the webcam clip, Smaller gave a WebM under half the size of the MP4. On the screen recording it changed nothing, because all three settings were already at the floor that keeps text readable. For anything with text on screen, Balanced is the right choice; use Smaller for footage of people and places where a little softness will not be noticed.

MP4	Smaller	Balanced	Best
Screen recording, 2.5 MB	8.5 MB	8.5 MB	8.5 MB
Webcam, 22.4 MB	9.9 MB	14.6 MB	18.1 MB

The same two MP4s at each Quality setting, in Chrome 155 on an M1 Mac. Each took 6 to 7 seconds.

Do you need WebM for a web page?

Usually not. An H.264 MP4 plays in every major browser, in a <video> element as well as anywhere else, so a single MP4 is enough for most sites. WebM earns its place when you want an open, royalty-free format, when a tool or platform asks for it, or when you serve a lot of video and VP9’s better compression saves bandwidth.

The common pattern is to offer both: a <source> with the WebM first and the MP4 second inside the same <video>. Each browser plays the first one it can, and nobody is left with nothing. For a short looping clip that replaces a GIF, add autoplay, muted, loop and playsinline.

When not to convert

Do not convert just to make a file smaller. As the table shows, a well-compressed MP4, especially a screen recording, can come out larger as a WebM. To shrink a video, use the video compressor, which keeps it an MP4.

Do not convert when the place it is going takes MP4. YouTube, social sites, chat apps and email all accept MP4, and some editors and phone photo libraries handle MP4 better than WebM. Converting adds a re-encode for nothing.

Converting cannot add quality or transparency. The WebM can only be as good as the MP4 it came from, and an MP4 has no transparent parts to carry over, so the background stays solid.

Other ways to convert MP4 to WebM

ffmpeg Any computer, from the command line

Install ffmpeg (on a Mac with Homebrew: brew install ffmpeg; on Windows: winget install Gyan.FFmpeg).
Run ffmpeg -i input.mp4 -c:v libvpx-vp9 -crf 31 -b:v 0 -row-mt 1 -c:a libopus -b:a 128k output.webm. Lower -crf for a sharper, larger file; 31 is Google’s suggestion for 1080p.

Makes smaller files than a browser at similar quality, but takes much longer: with these settings our screen recording became 2.7 MB in 57 seconds and the webcam clip 3.1 MB in 33 seconds on the same M1 Mac.

HandBrake Mac, Windows or Linux

Open HandBrake and choose the MP4 with Open Source.
On the Summary tab, set Format to WebM.
On the Video tab, set Video Encoder to VP9; on the Audio tab, choose Opus.
Choose where to save it and press Start Encode.

Free and open source, with a queue for converting a folder of files. Encoding is slow, like ffmpeg’s.

VLC Mac, Windows or Linux

Choose Media › Convert / Save (on a Mac, File › Convert / Stream) and add the MP4.
Pick the profile Video - VP80 + Vorbis (Webm), choose where to save it, and start.

Handy if VLC is already installed, but its ready-made WebM profile uses the older VP8 and Vorbis, which give larger files for the same quality.

Frequently asked questions

How do I convert MP4 to WebM?

Drop the MP4 on the converter at the top of this page and press Convert to WebM. It re-encodes the picture as VP9 and the sound as Opus in your browser, checks the result, and saves it under the same name ending in .webm. Nothing is uploaded.

How do I convert to MP4 without losing quality?

Copy the video instead of re-encoding it, which works when it is already H.264 or HEVC. The MOV to MP4 and MKV to MP4 converters do that and say “copied without re-encoding” when nothing was lost. Converting to WebM always re-encodes.

How do I convert WebM to MP4 on Windows?

Open the WebM to MP4 converter in Chrome or Edge on Windows and drop the file there; nothing to install. For many files, HandBrake for Windows does the same with Format set to MP4.

How can I convert HEVC video to MP4?

An iPhone’s HEVC video is usually a MOV: the MOV to MP4 converter copies the HEVC into an MP4 as it is, or re-encodes it as H.264 for Windows and older players. For WebM, the browser has to decode HEVC first: Safari on a Mac can, and Chrome or Edge can on most computers; Firefox cannot, and this page says so before you choose a file.

What is the best MP4 converter?

It depends on the job. For one file, a browser converter like this one is quickest and installs nothing. For a folder of files, HandBrake. For scripts or exact settings, ffmpeg. Whichever you use, prefer one that copies the video when it can rather than always re-encoding.

Where can I download a free HEVC to MP4 converter?

HandBrake is free and open source for Mac, Windows and Linux, from handbrake.fr, and it turns HEVC into H.264 MP4. Or skip the download: the MOV to MP4 converter does it in your browser.

Why did my WebM come out bigger than the MP4?

Because the MP4 was already very efficient, which is typical of screen recordings where most of the picture stands still. The converter keeps a minimum bitrate so text stays readable, and that minimum can be more than the original used. Keep the MP4 in that case: it is the better file.

Is my file uploaded?

No. Your MP4 is read, converted and checked on your own computer, so there is no upload and no queue. In Chrome and Edge on a computer files of any size work, written straight to a file you choose; in other browsers, files up to 2.0 GB. We count anonymous page views and whether a conversion worked; when one fails, the event also carries the step, your browser’s error and the file’s codecs, size and length in broad bands, never the file or its name. If a conversion fails you can choose to send us the file, which is deleted within 30 days. See the privacy policy.

Spend less time editing
your next recording.

Create an account and record your first video in your browser.

No credit card required