WebM to MP3 Converter
Turn a WebM file into an MP3 that plays everywhere. WebM is what browser screen recorders and many downloads save, and many players and phones will not play it.
- Free, no sign-up
- Runs in your browser
- Nothing uploaded or kept
Drop videos or audio here
or choose them from your device, as many as you like: MP4, MOV, MKV, WebM, M4A, WAV…
- Converted on your device. Nothing is uploaded
- No limits on file size or number of files
- Trim, fade, even out the volume and add song details
More options
How to use it
Choose your WebM
Drop one or more .webm, .mkv or .ogg files on the box. Nothing is uploaded.
Set the quality
192 kbps for music, 128 kbps for speech. Tap the scissors to trim.
Download your MP3s
Each file converts as soon as it is added. Download one, or a ZIP of them all.
This works in your browser, so the file is never uploaded, and MKV and Ogg Opus files convert here too.
Why convert your video here
Most online converters upload your video to a server, limit its size or how many files you can do, and put a limit or an advert in the way. This one does none of that, because the conversion is done by your own browser.
- Your video never leaves your device. The file is read from your disk and turned into an MP3 on this page. Open the Network tab in your browser's developer tools while you convert one to see for yourself: no request carries your file.
- No watermark, no sign-up, no limits. No daily cap, no limit on the size or number of files, and no wait for an upload. A one-hour recording converted in 68 seconds in our test.
- Trim on a waveform. See the sound, drag the two handles, type exact times down to a hundredth of a second, and play the part you chose before you convert it.
- Even out the volume. Every file can be brought to the same loudness, measured the way streaming services do it, without the peaks ever clipping.
- Song details and a cover picture. Set the title, artist and album, and a cover from a frame of the video or your own picture, so a phone or music player shows them.
- The right sound track and proper surround. A film with several languages lets you choose one by name. 5.1 and 7.1 sound is mixed down to stereo with the dialogue kept.
- Exact lengths. The MP3 carries its true length in its header, so a player does not add a gap at the end.
- Many at once. Drop a whole folder; each file converts as soon as it is added, and you can download a ZIP that keeps your folders.
Why convert WebM to MP3
WebM files come from browser recorders, screen-capture tools and downloads. Their sound is usually Opus, a modern format that many phones, car stereos and music apps do not play. An MP3 plays on nearly everything. MKV files, which hold the same kinds of sound, convert here too, and so do Ogg Opus audio files.
What each setting does
| Setting | What it does |
|---|---|
| Convert to | MP3, or WAV (lossless). A WAV keeps the sound exactly as decoded, at the file's own sample rate, and is far bigger. |
| Quality | 320, 256, 192 (the default), 160, 128, 96 or 64 kbps. 192 suits music; 128 suits speech. Choosing more than the file's own sound can use only makes the file bigger, and the converter tells you when that happens. |
| Volume | Keep as it is, or Even out (like Spotify): brings the file to -14 LUFS with the peaks held under -1.5 dB. Even out reads a long file twice, so it takes about twice as long. |
| Channels | Stereo as the file, or Mono. Mono makes the MP3 half the size: the quality you pick is for stereo, and mono uses half of it. A mono video stays mono. |
| Fade in and fade out | None, or 1, 2, 3, 5 or 10 seconds, with a smooth curve rather than a straight ramp. |
| Trim (the scissors) | Start and End on a waveform, with keyboard control and exact typed times to 0.01 s, and Play selection to hear it first. |
| Sound track | For files with more than one, the list names each track by language and codec. |
| Song details | Title, artist and album, then a cover picture from a video frame, the file's own picture or one you choose. |
Quality, Volume and Convert to are remembered for your next visit. Mono and the fades are not, because they change the sound itself and would otherwise quietly apply to the next file you convert.
How it works
Your browser opens the file where it is and reads only its sound. Where the browser can decode the sound itself, it does so with the same decoder it uses to play it. Where it cannot, the sound is copied, without decoding, into a form the browser's own audio player reads, and decoded there; that is slower and limited to about 28 minutes of stereo at a time, and a longer file asks you to choose a shorter part.
The sound is then mixed down to stereo if it has more channels, shaped with your volume and fades, and passed to LAME, the standard MP3 encoder, which runs in a background worker so the page stays responsive. LAME is free software under the LGPL licence and is loaded as a separate file; its licence and source link are on the open-source licences page.
Loudness is measured once with the ITU-R BS.1770 method (the one streaming services use), in 100 millisecond pieces, so the loudness of any part you choose to keep is worked out without reading the file again, and the same pass draws the waveform.
How we tested it
Before release, the converter was run in Chrome 156 on a Windows PC with 8 processor cores, using test files with known content that we made for the job: a different tone in the left and right channels (to catch swapped channels), 5.1 and 7.1 files with one tone per speaker, a file with two languages, Opus in WebM, a MOV, raw AAC, Ogg Opus, MPEG-TS, 96 kHz and 22.05 kHz sound, a video with no sound, and a text file renamed .mp4.
Every MP3 was then decoded by Chrome's own MP3 decoder, not by this tool's code, and measured:
- The left and right tones came out in the right channels, within 0.7 dB of their level in the source, with nothing leaking across (under -45 dB, usually under -85 dB).
- Lengths were exact: a 6 second file made exactly 288,000 samples, and a 4 second 96 kHz file exactly 192,000 at 48 kHz.
- 5.1 and 7.1 files mixed down with the dialogue in both speakers and the effects channel left out.
- Trims kept exactly the part chosen (5.000 s from a stepped-tone file, with the right tones at the start and end), and fades were silent at the edges.
- Even out brought a -40 LUFS recording to -14.3 LUFS, measured with the coefficients published in the standard; Keep as it is left it at -40.3.
- WAV output was identical, sample for sample, to a 16-bit source.
- Titles, artists and albums with accents and symbols, and a custom cover picture, were written and read back correctly, and a ZIP of four files passed its integrity check and kept folder names.
- With the browser's sound decoders switched off, every test file still converted, with the same results.
- Converting wrote no request carrying the files; the site's analytics requests were far too small to hold them and contained none of their bytes.
Speed, on the same PC: 10 minutes of sound converted in 10 seconds, and a one-hour stereo recording (a 58 MB file) in 68 seconds at 192 kbps, or 125 seconds with Even out. The page used about 50 MB of JavaScript memory for the hour. Your device may be faster or slower.
Not tested yet: real phones (Safari on iPhone, Chrome on Android), Firefox and Safari on a computer, FLAC files (Chrome cannot make a FLAC file to test with), and Dolby Digital or DTS sound. They use the same code; if something does not work for you, tell us which browser and what kind of file.
More free tools for videos and pictures
The same converter, with help for other files: MP4 to MP3 converter, Video to MP3 converter, MOV to MP3 converter and MP4 to WAV converter. To make a short silent clip instead, MP4 to GIF turns any part of a video into a GIF, and for photos, HEIC to JPG and WebP to JPG work in your browser too.
Frequently asked questions
Is my file uploaded to a server?
No. The sound is taken out of your video and turned into an MP3 inside your browser, on your own device: the file is read from your disk and never sent anywhere. Nothing is stored on a server and nobody else can see it. You can check: open your browser's developer tools, go to the Network tab, and convert a file; no request carries your video or your audio.
How do I convert a WebM to an MP3?
Drop the .webm on the box above or tap Choose files. It is converted to a 192 kbps MP3 at once; download it when it is done. Tap the scissors beside it to keep only part of the sound.
What is a WebM file?
WebM is an open format for video on the web, with VP8, VP9 or AV1 video and Opus or Vorbis sound. Browser screen recorders, OBS and many downloads save it. Plenty of phones, car stereos and apps will not play it, which is where an MP3 still works everywhere. We tested a WebM with VP9 video and Opus sound, and Ogg Opus audio files.
Is the video decoded too?
Yes, only the sound is read; the picture is skipped. In a browser that cannot decode sound directly (some phones' browsers are like this), the sound is first copied into a form the browser's own audio player can read and then converted. We tested that route with the same files and the results were the same.
Is there a size limit or a watermark?
No. There is no watermark, no sign-up, no daily limit and no limit on how big a file is or how many you add. Because nothing is uploaded there is no upload wait. In our test, a one-hour stereo recording (a 58 MB file made for the test) became a 192 kbps MP3 in 68 seconds on a Windows PC with 8 processor cores, using Chrome; an older phone will take longer.
Do MKV and Ogg files work too?
Video files in MP4, MOV, MKV, WebM and MPEG-TS (.ts), and audio files in M4A, MP3, WAV, raw AAC and Ogg Opus. The sound can be AAC, Opus, Vorbis, MP3 or uncompressed PCM, wherever your browser can decode it. We tested every one of those; we could not test FLAC (Chrome cannot make a FLAC file to test with), so FLAC is accepted but not proven. Dolby Digital (AC-3) and DTS sound can usually not be decoded by a web browser; the converter then says so, and if the film has another sound track you can choose that one.
Can I convert only part of it?
Yes. Tap the scissors beside a file to open its editor. Drag the two handles on the waveform, or use the arrow keys (Shift for whole seconds), or type exact start and end times down to a hundredth of a second, then tap Play selection to hear it. Tap Save and convert and only that part is made into an MP3. Fade in and fade out (1 to 10 seconds) are under More options.
Can I convert many files at once?
Yes. Drop as many files as you like, or choose a whole folder on a computer. Each one starts converting as soon as it is added, two at a time on a computer with four or more processor cores, and you can download them one by one or all together in a ZIP that keeps your folder structure. Files are listed in name order.
What does Even out the volume do?
It measures how loud each file sounds, the way streaming services do (the ITU-R BS.1770 / EBU R128 method), and turns it up or down to -14 LUFS, the level Spotify and YouTube play at. Peaks are held under -1.5 dB, so nothing distorts; a very dynamic recording can end up a little quieter than -14 LUFS for that reason. In our test a very quiet recording (-40 LUFS) came out at -14.3 LUFS, measured separately with the coefficients published in the standard.
Does converting to MP3 lose quality?
MP3 is a lossy format, so every MP3 is a little different from the sound it came from, and a video's sound is usually already compressed (AAC), so converting to MP3 compresses it a second time. At 192 kbps or more the difference is very hard to hear in normal listening. If you need the sound exactly as it is in the video, choose WAV.
Does it work on iPhone and Android?
It should: it uses Safari on iPhone and iPad and Chrome on Android, with nothing to install. Choose a video from your photos or files, and when it has converted tap Share to save the MP3 to Files or send it to another app. We have not been able to test it on real phones yet, so if something does not work, tell us which phone and browser. Long files need memory, so on an older phone convert a shorter part.
A free tool from LetRelay: no sign-up, nothing stored on a server.