How to convert MP4 to MP3 in your browser
Extract the main audio track from a video. Choose an MP3 bitrate, check codec support and download a copy you can keep.
Choose one MP4, MOV or WebM video up to 300 MB and 20 minutes. Keep the default 192 kbps or choose another bitrate, then convert and download the MP3. The selected video is processed on your device.
Convert the video in five steps
Choose the local video
Open the converter and select one MP4, MOV or WebM file within the 300 MB limit.
Confirm the audio and duration
Check the detected audio track and duration. It must contain decodable audio and be no longer than 20 minutes.
Choose an MP3 bitrate
Keep 192 kbps for a general listening copy. Choose 128 kbps for a smaller file or 320 kbps for the highest available encoding target.
Convert without closing the tab
Start conversion and keep the page open while the browser encodes the main audio track.
Download and check the result
Play the beginning, middle and end. Download the MP3 when it is ready; you do not need to wait for local history to save.
Choose an MP3 bitrate
A higher bitrate creates a larger file. It cannot restore detail missing from the source. Start with 192 kbps unless file size or a destination requirement points you elsewhere.
The sizes below are estimates for ten minutes of audio, before small file overheads. Duration and bitrate determine most of the output size.
| Bitrate | Good starting point | Approximate size per 10 minutes |
|---|---|---|
| 128 kbps | Speech, interviews and compact copies | About 9.6 MB |
| 192 kbps | Balanced default for voice and music | About 14.4 MB |
| 320 kbps | Largest output and highest available target | About 24 MB |
What the MP3 keeps
The output is a separate audio-only file; the source video stays unchanged. The converter uses the main audio track. It does not trim silence, remove noise, normalize loudness or edit ID3 tags.
Mono stays mono and stereo stays stereo. More than two channels are downmixed to stereo.
The download keeps the source name with an .mp3 extension: interview.final.mp4 becomes interview.final.mp3.
| Source detail | MP3 result |
|---|---|
| Main audio track | Decoded and encoded as MP3 |
| Video and picture | Discarded |
| Mono or stereo channels | Kept as mono or stereo |
| More than two audio channels | Downmixed to stereo |
| Original source quality | Cannot be improved by selecting a higher bitrate |
| Captions, chapters and video metadata | Not transferred into MP3 tags |
An extension is not a codec
MP4, MOV and WebM are containers. The audio codec inside still needs browser support. A supported filename alone does not guarantee conversion.
If no readable track is found, play the source to confirm it has sound. Try another browser or re-export the source with a supported audio codec. Renaming the extension does not change the codec.
The converter accepts one local file at a time. Shorten or split videos above 300 MB or 20 minutes in another editor; pasted URLs and batch conversion are not supported.
Network requests and local history
Your selected video is converted in this browser. The source video and temporary decoded audio are not saved in conversion history.
The application, fonts and encoder resources still download. Optional analytics connects after consent; product events exclude selected media, filenames and MP3 content.
Download the MP3 before leaving. Whisper Web also tries to save it in this browser for up to 30 days, but browser data can be cleared sooner. If history saving fails, the current MP3 remains available for download.
| Item | Where it goes |
|---|---|
| Selected MP4, MOV or WebM | Read and decoded on the current device; not added to history |
| Decoded working audio | Used temporarily during conversion; not saved as a history item |
| Completed MP3 | Available in page memory and saved to local browser history after success |
| Application and encoder resources | Downloaded as needed when the site loads or conversion starts |
| Optional analytics | After consent, receives registered pages and predefined usage categories; product events exclude media, filenames and MP3 content |
Cancel or restart a conversion
Cancel stops the current job. Wait for it to finish stopping, then adjust the bitrate or start again. The selected video remains; an unfinished MP3 is not added to history.
Refreshing or closing the tab loses the unfinished job. Conversion history is not a checkpoint: select the source again to restart. Processing time depends on the recording and current device load.
| What happens? | What is kept? | Next step |
|---|---|---|
| You cancel conversion | The selected video remains; no MP3 or history record is created | Choose a bitrate and try again |
| You refresh or close the tab | The unfinished conversion is lost | Select the source again and restart |
| Local history cannot be saved | The completed MP3 remains available for immediate download | Download it before leaving the page |
| Conversion completes | The MP3 is downloaded on request and saved to local history | Play, search, download again or delete it |
When conversion does not work
| Problem | Likely reason | What to check |
|---|---|---|
| The file is rejected before analysis | It is not MP4, MOV or WebM, or exceeds 300 MB | Choose a supported local video within the size limit |
| No readable audio track | The video is silent or its audio codec is not supported by this browser | Play the source, try a current desktop browser or re-export the audio track |
| The video is over 20 minutes | The audio duration exceeds the converter limit | Shorten or split it before conversion |
| The MP3 sounds no better at 320 kbps | The source already lacks that detail | Use a cleaner source; bitrate cannot recreate lost quality |
| Conversion is slow | Encoding uses the current device | Keep the tab open, connect to power and reduce other heavy work |
| The result disappeared later | Browser storage was cleared or the 30-day retention period ended | Download important MP3 files instead of treating history as a backup |
Check the MP3 before using it
Play several points in the file
Listen at the beginning, middle and end for silence or an unexpected audio track.
Confirm the destination accepts MP3
Check the receiving player, editor or upload form for audio-format and size limits.
Download a durable copy
Save the MP3 to a folder or backup you control. Browser history is temporary storage.
Transcribe only when text is the goal
Conversion creates audio, not text. For a transcript or captions, use the transcription tool with the source video or completed MP3.
Common questions
Can I convert MP4 to MP3 without uploading the video?
Yes. Whisper Web reads, decodes and encodes a selected local video in the current browser rather than uploading it to a Whisper Web conversion server. The page and encoder resources still require ordinary network requests.
Which video formats can I convert?
The current converter accepts one local MP4, MOV or WebM file up to 300 MB and 20 minutes. Actual decoding still depends on the audio codec and browser support.
Is 320 kbps always better than 192 kbps?
It uses a higher encoding target and creates a larger file, but it cannot recover audio detail missing from the source. The 192 kbps default is the balanced choice for most general video audio.
Does converting MP4 to MP3 reduce the video file size?
The converter creates a separate audio-only MP3 and leaves the source video unchanged. The MP3 is usually smaller because it does not contain the video track, but its size depends mainly on duration and selected bitrate.
Can I convert a video longer than 20 minutes?
Not in the current converter. Shorten or split the video into sections of 20 minutes or less, with each file no larger than 300 MB, before importing it.
Can I convert several MP4 files at once?
No. The converter handles one local file at a time and does not provide batch conversion.
Where can I find a completed conversion?
Download it as soon as conversion finishes or open Conversions history in the same browser. Completed MP3 files remain there for up to 30 days unless the browser clears site storage earlier or you delete them.
Does the converter create a transcript?
No. It extracts and encodes the main audio track as MP3. Use Whisper Web transcription when you need editable text, timestamps, SRT or VTT captions.