Live
MKV to MP4
Play an MKV on anything, without re-encoding it
WebM to MP4
LiveConvert a WebM into an MP4 that phones, TVs, editing software and older Windows players will open. Unlike our MOV and MKV pages, this one is always a genuine conversion rather than a repackage, because nothing a WebM holds can be carried into an MP4 untouched. The page says what that costs instead of implying it is free.
What it does
- Re-encodes VP8, VP9 and AV1 video to H.264 and Vorbis or Opus sound to AAC
- Three quality levels that are actually used here, unlike on a MOV or an H.264 MKV
- Tells you the size it came out at rather than promising a percentage it cannot know
Your files
Gone within the hour.
Files are uploaded over HTTPS, used only to run this tool, and deleted from our server automatically about an hour later. Never sold, never used to train anything.
How to convert a WebM to MP4
Drop the WebM in
Use the box above, or click it to browse. One file per job, up to 50 MB, and up to 20 minutes of running time. A WebM out of a screen recorder or a browser download is the ordinary case.
Choose a quality level, because this one uses it
Higher quality, Balanced or Smaller file. On our MOV and MKV pages this setting is often ignored, since those files are usually copied rather than compressed. Here it is read on every job, because the picture is always encoded again. Balanced is the default and is the right answer for a screen recording.
Press Convert to MP4
This takes roughly as long as the video runs, rather than the second a repackage takes. That is the honest cost of the format change and not a queue: there is no daily allowance on this tool and nothing to wait behind.
Check the size before you send it on
The result screen reports what the MP4 actually came out at. A heavily compressed WebM can come back larger than it went in, which is worth seeing before you attach it to an email.
Frequently asked questions
Does converting WebM to MP4 lose quality?
Yes, and anyone telling you otherwise about a WebM specifically is wrong. A container change can be free: lift the encoded video out of one box and put it in another, which is what happens to most MOV files on our MOV page. It cannot be free here. WebM is defined around VP8, VP9 and AV1 video with Vorbis or Opus sound, and none of those can be relied on to play from inside an MP4, so the picture is decoded and encoded again as H.264 and the sound as AAC. That is one extra generation of lossy compression. At the default level the difference is hard to see on a screen recording or a talking head, and it is real, so keep the WebM if you might edit or re-export the footage later.
Will the MP4 be bigger or smaller than my WebM?
Either, and this page will not quote you a percentage because the honest answer depends on your file. VP9 is a more efficient codec than H.264, so a WebM that was already squeezed hard has little room left and re-encoding it to H.264 usually makes it bigger. A WebM saved at a generous bitrate has room to spare and tends to land about the same or smaller. Measured on 2026-09-25 by putting real files through the worker: a 320x240 VP9 and Opus clip at 200 kbps went from 89,253 to 147,069 bytes, up 65 percent, while a 1280x720 VP9 clip at 4,000 kbps went from 1,355,678 to 1,354,429 bytes, which is unchanged. Same tool, same setting, opposite outcomes. The result screen reports the real figure for your file, and Compress Video is the tool to reach for if what you need is smaller rather than more compatible.
Why convert a WebM at all if it already plays in my browser?
Because the browser is the one place it reliably works. WebM came out of the web and Chrome, Firefox and Edge all play it, which is why a screen recorder or a browser download hands you one. Outside the browser it runs out of support quickly: video editing software often refuses it, television sets and set-top boxes commonly will not open it, older Windows players do not, and sending one to someone on an unknown device is a gamble. MP4 with H.264 and AAC is the closest thing to a format everything opens, which is the whole reason for the trade this page makes.
Does the quality setting actually do anything here?
Yes, on every job, and that is a real difference from our sibling pages rather than a sales point. The three levels set how hard the new H.264 picture is compressed, and they are only consulted when the picture has to be encoded. On a MOV from a phone or an MKV holding H.264 that never happens, so the setting sits there unused. A WebM always takes the encode path, so the level you pick is read every time. Smaller file compresses hardest, Balanced is the default, and Higher quality compresses least and produces the largest file.
What happens to a second audio track or the subtitles?
They are not carried over. The job takes the first video track and the first audio track and nothing else, so a second audio language is dropped, any subtitle track is dropped, and the title and track names stored in the container are stripped. A WebM with no sound at all is fine and comes back as a silent MP4 rather than being refused. This matters less on WebM than on MKV, since a browser recording rarely has more than one of each, but it is true here too and is stated rather than left for you to discover.
How big and how long can the WebM be?
One file per job, up to 50 MB, and up to 20 minutes of running time, with the finished MP4 also having to come in under 500 MB. A file over the size limit is refused as soon as it is uploaded, and one over the time limit is refused with a message naming the limit rather than being left to fail halfway. Your WebM and the MP4 it produces are both deleted from our server automatically about an hour later. There is no account and no watermark.