# Convert AAC to M4B

> Convert AAC to M4B online for free. Runs entirely in your browser, so your files never leave your device. Fast batch conversion, no sign-up, no watermarks.

URL: https://www.converterrr.com/aac-to-m4b

- Runs in the browser with FFmpeg (WASM): files are not uploaded, and no credits are used.
- Engines: FFmpeg (WASM) (browser), FFmpeg (cloud).
- API: available. `POST /api/v1/jobs` with `"output_format": "m4b"` (paid plans).
- More: [Audio converter](https://www.converterrr.com/audio-converter), [AAC converter](https://www.converterrr.com/aac-converter), [Compress AAC](https://www.converterrr.com/compress-aac).

## How to convert AAC to M4B

1. **Add your AAC files.** Drag and drop AAC files onto the converter, paste them, or click to browse. You can add several at once.
2. **Choose M4B.** M4B is already selected. Open Options if you want to change quality, size or metadata.
3. **Convert.** Click Convert. Your files are converted right in your browser in seconds.
4. **Download your M4B.** Download each M4B file, or everything at once as a ZIP.

## Good to know

- We encode at a high-quality bitrate by default. Pick a specific bitrate or sample rate under Options.
- AAC files are typically used for streaming, mobile audio and video soundtracks, while M4B is best for audiobooks on Apple Books and other players.
- This conversion runs on FFmpeg (WASM), running locally in your browser — nothing is uploaded and it works even on slow connections.

## AAC vs M4B

|  | AAC | M4B |
| --- | --- | --- |
| Full name | Advanced Audio Coding | MPEG-4 Audiobook |
| Type | Audio | Audio |
| Extensions | .aac | .m4b |
| MIME type | audio/aac | audio/mp4 |
| Best for | streaming, mobile audio and video soundtracks | audiobooks on Apple Books and other players |
| Properties | lossy compression | lossy compression |

**AAC:** AAC is the successor to MP3, delivering better quality at the same bitrate. It's the default audio codec on Apple devices and YouTube.

**M4B:** M4B is an MP4 audio file flagged as an audiobook, supporting chapters and resume position.

The other way around: [convert M4B to AAC](https://www.converterrr.com/m4b-to-aac).

## Related conversions

- [M4B to AAC](https://www.converterrr.com/m4b-to-aac) (in the browser)
- [AAC to MP3](https://www.converterrr.com/aac-to-mp3) (in the browser)
- [MP3 to M4B](https://www.converterrr.com/mp3-to-m4b) (in the browser)
- [AAC to WAV](https://www.converterrr.com/aac-to-wav) (in the browser)
- [MP4 to M4B](https://www.converterrr.com/mp4-to-m4b) (in the browser)
- [AAC to M4A](https://www.converterrr.com/aac-to-m4a) (in the browser)
- [WAV to M4B](https://www.converterrr.com/wav-to-m4b) (in the browser)
- [AAC to FLAC](https://www.converterrr.com/aac-to-flac) (in the browser)
- [MOV to M4B](https://www.converterrr.com/mov-to-m4b) (in the browser)
- [AAC to OGG](https://www.converterrr.com/aac-to-ogg) (in the browser)
- [M4A to M4B](https://www.converterrr.com/m4a-to-m4b) (in the browser)
- [AAC to Opus](https://www.converterrr.com/aac-to-opus) (in the browser)

## Convert AAC to other formats

[AAC to MP3](https://www.converterrr.com/aac-to-mp3), [AAC to WAV](https://www.converterrr.com/aac-to-wav), [AAC to M4A](https://www.converterrr.com/aac-to-m4a), [AAC to FLAC](https://www.converterrr.com/aac-to-flac), [AAC to OGG](https://www.converterrr.com/aac-to-ogg), [AAC to Opus](https://www.converterrr.com/aac-to-opus), [AAC to WMA](https://www.converterrr.com/aac-to-wma), [AAC to AIFF](https://www.converterrr.com/aac-to-aiff), [AAC to AMR](https://www.converterrr.com/aac-to-amr), [AAC to AC3](https://www.converterrr.com/aac-to-ac3), [AAC to MP2](https://www.converterrr.com/aac-to-mp2), [AAC to WEBA](https://www.converterrr.com/aac-to-weba), [AAC to OGA](https://www.converterrr.com/aac-to-oga), [AAC to MKA](https://www.converterrr.com/aac-to-mka), [AAC to WV](https://www.converterrr.com/aac-to-wv), [AAC to AU](https://www.converterrr.com/aac-to-au), [AAC to TTA](https://www.converterrr.com/aac-to-tta)

## Convert other formats to M4B

[MP3 to M4B](https://www.converterrr.com/mp3-to-m4b), [MP4 to M4B](https://www.converterrr.com/mp4-to-m4b), [WAV to M4B](https://www.converterrr.com/wav-to-m4b), [MOV to M4B](https://www.converterrr.com/mov-to-m4b), [M4A to M4B](https://www.converterrr.com/m4a-to-m4b), [WebM to M4B](https://www.converterrr.com/webm-to-m4b), [FLAC to M4B](https://www.converterrr.com/flac-to-m4b), [MKV to M4B](https://www.converterrr.com/mkv-to-m4b), [AVI to M4B](https://www.converterrr.com/avi-to-m4b), [OGG to M4B](https://www.converterrr.com/ogg-to-m4b), [WMV to M4B](https://www.converterrr.com/wmv-to-m4b), [Opus to M4B](https://www.converterrr.com/opus-to-m4b), [WMA to M4B](https://www.converterrr.com/wma-to-m4b), [FLV to M4B](https://www.converterrr.com/flv-to-m4b), [M4V to M4B](https://www.converterrr.com/m4v-to-m4b), [MPEG to M4B](https://www.converterrr.com/mpeg-to-m4b), [3GP to M4B](https://www.converterrr.com/3gp-to-m4b), [AIFF to M4B](https://www.converterrr.com/aiff-to-m4b), [AMR to M4B](https://www.converterrr.com/amr-to-m4b), [MPG to M4B](https://www.converterrr.com/mpg-to-m4b), [TS to M4B](https://www.converterrr.com/ts-to-m4b), [MTS to M4B](https://www.converterrr.com/mts-to-m4b), [VOB to M4B](https://www.converterrr.com/vob-to-m4b), [M2TS to M4B](https://www.converterrr.com/m2ts-to-m4b)

## AAC to M4B: frequently asked questions

### How do I convert AAC to M4B?

Drop your AAC file onto the converter above, make sure M4B is selected, and click Convert. When it's done, download the M4B file — it usually takes a few seconds.

### Is it safe to convert AAC to M4B here?

Yes. AAC to M4B conversion happens entirely inside your browser using WebAssembly, so your file is never uploaded to any server.

### Is the AAC to M4B converter free?

Yes — free with no watermark. Signed-out visitors can convert 25 files a day, and a free account raises that to 250.

### Will converting AAC to M4B reduce quality?

M4B is a lossy format, but our defaults are tuned to be visually indistinguishable for most files. You can raise the quality under Options.

### Can I convert multiple AAC files at once?

Yes. Add up to 5 files at a time without an account, 10 with a free account and up to 500 on paid plans, then download them individually or as a single ZIP.

### Can I convert M4B back to AAC?

Yes — use our M4B to AAC converter. Note that converting back and forth between formats can't recover detail lost to lossy compression.