AAC to M4B converter
A free AAC to M4B converter for Advanced Audio Coding files. Browser-based pairs here usually run in this tab, with no file upload.
Drop your AAC files here
or browse your device · paste with Ctrl+V
Accepts .aac, .adts 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 AAC 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.
AAC
Advanced Audio CodingMP3's designated successor and the audio inside almost every MP4, YouTube stream and Apple Music track. At 128 kbps it comfortably beats MP3 at the same bitrate.
- Developed by
- ISO/IEC (MPEG)
- Released
- 1997
- Extension
- .aac, .adts
- MIME type
- audio/aac
- 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 AAC 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 AAC to M4B
Is this AAC to M4B converter free?
Yes. Converting AAC 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 AAC 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 AAC 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 AAC 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 AAC file if you might need it again.
Can I convert several AAC 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 AAC 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 AAC to other formats
A AAC file can become any of these.
M4B to AAC
The reverse conversion
AAC to MP3
AAC to WAV
AAC to FLAC
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…