MP3 to M4B converter
A free MP3 to M4B converter for MPEG-1 Audio Layer III files. Browser-based pairs here usually run in this tab, with no file upload.
Drop your MP3 files here
or browse your device · paste with Ctrl+V
Accepts .mp3 files. You can queue several files; each is processed one after another on your own device.
Your files never leave this device — there is no upload and no server to delete them from.
- 01
Add your MP3 files
Drop them onto the box above or click to browse. They are read straight from disk — nothing is sent anywhere.
- 02
Check the settings
M4B is already selected. Open the gear icon on any row if you want to change quality, dimensions or codec before converting.
- 03
Download your M4B
Press convert and wait for the row to finish. Convert several files and you can take them all as a single ZIP.
MP3
MPEG-1 Audio Layer IIIThe format that made digital music portable, and still the most universally playable audio file in existence. Its patents expired in 2017, so it is now free to use everywhere. 192–320 kbps is transparent enough for almost any listener.
- Developed by
- Fraunhofer IIS
- Released
- 1993
- Extension
- .mp3
- MIME type
- audio/mpeg
- Compression
- Lossy
M4B
MPEG-4 AudiobookAn M4A that flags itself as an audiobook, so players remember your position and honour chapter markers. Audible titles land here once stripped of DRM.
- Developed by
- Apple
- Released
- 2003
- Extension
- .m4b
- MIME type
- audio/mp4
- Compression
- Lossy
- Both MP3 and M4B are lossy formats, so repeated conversions can accumulate rounding artifacts. Keep this to only what you need and avoid repeated round-trips.
Questions about converting MP3 to M4B
Is this MP3 to M4B converter free?
Yes. Converting MP3 to M4B here is free, with no account, no watermark and no daily quota. The work runs on your own device, so there is no server cost to pass on to you.
Is my MP3 file uploaded anywhere?
For browser-based pairs, your file is read locally and converted by ffmpeg in this tab. No file payload is uploaded; you may still see analytics and engine downloads in network logs.
Is there a file-size limit for MP3 to M4B?
There is no imposed upload cap when it runs in-browser, but each conversion still depends on your device and browser memory. Large videos are the first practical limit, then memory-heavy documents or images.
Does converting MP3 to M4B lose quality?
M4B is a lossy format, so some detail is discarded when it is encoded. At the default quality setting the change is often not visually obvious; keep your original MP3 file if you might need it again.
Can I convert several MP3 files to M4B at once?
Yes. Drop in several files and each gets its own row; they are processed one after another on your device. You can download them one by one or as one ZIP.
Does MP3 to M4B work on a phone, Mac or Chromebook?
Most modern browsers on Windows, macOS, Linux, ChromeOS, Android and iOS work. Very large videos are often more reliable on desktop or a browser with more memory.
Why do some conversions take longer on first run?
The conversion engine has to download first. Small codec bundles are fast, while ffmpeg is commonly 12–30 MB; later conversions of similar type use the cached engine.
I converted a file and the output is blank or unusable. What should I check?
Start over with default settings, then change one option at a time (quality, bitrate, page size, or codec) to isolate what changed behavior. If it keeps failing, retry with a smaller file and confirm the source format matches the pair.
Convert other formats to M4B
41 formats can become M4B here.
Convert MP3 to other formats
A MP3 file can become any of these.
M4B to MP3
The reverse conversion
MP3 to WAV
MP3 to FLAC
MP3 to M4A
Extract Audio from Video
Pull the soundtrack out of a video as an MP3.…
Compress Audio
Lower the bitrate of audio files to save space.…
Trim Audio
Cut a section out of an audio file.…
Normalise Audio
Even out loudness across files so nothing is jarring…