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How to convert MP4 to MP3 in your browser

By Lawal Ayo, LAS G Concept · Updated 15 October 2026

You have a video (a sermon, a lecture, a music video, a recorded call) and you only want the sound. Converting MP4 to MP3 gives you a much smaller file that plays on any phone, car stereo or MP3 player. This guide shows how to do it with LAS Converter, what the settings mean, and where the limits are.

The conversion runs inside your browser using ffmpeg.wasm. Your video is not uploaded to our server, which is why it works on a slow connection once the page has loaded, and why your private recordings stay on your device.

Step by step

Open the converter and log in. A free account is enough for MP3 conversion.
Choose Video → Audio in the left menu (or Convert if you want to pick the target format yourself).
Drop your MP4 on the box, or press browse and pick the file. The website accepts files up to 500 MB; for larger files use the Windows app.
Set the output format to MP3. The other choices in the list are FLAC, WAV, M4A, OGG and OPUS.
Pick a bitrate. The options are 128, 192, 256 and 320 kbps. On the free plan the maximum is 192 kbps; 256 and 320 are marked with a crown and need Premium.
Choose the channel layout: Original, Stereo or Mono. Mono is labelled "voice optimal" and is a good pick for speeches and interviews.
Press convert, wait for the progress bar to finish, then save the MP3.

Which bitrate should I choose?

Bitrate is how much data is used for each second of sound. A higher number sounds better and makes a bigger file. As a rough guide, a 4-minute song is about 3 MB at 128 kbps, about 5.5 MB at 192 kbps and about 9 MB at 320 kbps.

128 kbps: fine for speech, sermons and lectures where file size matters more than detail.
192 kbps: a good all-round choice and the highest the free plan allows. Most people cannot tell it from 320 kbps on phone speakers or earphones.
256 or 320 kbps: for music you want to keep, or for playing on good speakers. Premium only.

If your source video already has low-quality audio, a high bitrate will not improve it. You just get a bigger file with the same sound.

Tips for better results

If the video is a talk with one speaker, choose Mono. The file is about half the size and the voice stays clear.
Close other heavy tabs before converting a large file. ffmpeg.wasm uses your device memory, and a very large video can freeze a phone browser.
Use the extract audio guide if you want to keep the original audio without re-encoding, for example as M4A or OPUS.
Want to turn the audio into text afterwards? See how to transcribe Yoruba, Hausa and Pidgin audio.

Common problems

"File too large for the browser." The website limit is 500 MB per file. Use the free Windows app for bigger videos, or trim the video first.

The tab freezes or the page reloads. Your device ran out of memory. Try a smaller file, close other tabs, or use a laptop instead of a phone.

The MP3 has no sound. Some screen recordings have no audio track. Open the file in a player first to confirm it has sound, or use the Media Inspector in the app to see its audio streams.

Frequently asked questions

Is my video uploaded anywhere?

No. MP4 to MP3 conversion runs in your browser, so the file stays on your device.

Is it free?

Yes, MP3 conversion is included in the free plan with MP3 up to 192 kbps. 256 and 320 kbps need Premium.

Can I convert many videos at once?

Batch conversion is a Premium feature. On the free plan, convert one file at a time.

Does it work on my phone?

Yes in a modern mobile browser, or you can install the Android app. Large files are easier on a computer.

Try it

Use the Video to MP3 converter page to learn more, or go straight to the app.

Open the converter Create a free account