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.

M4B→AAC AAC→MP3 MP3→M4B AAC→WAV MP4→M4B AAC→M4A WAV→M4B AAC→FLAC MOV→M4B AAC→OGG M4A→M4B AAC→Opus AAC→WMA AAC→AIFF AAC→AMR AAC→AC3 AAC→MP2 AAC→WEBA AAC→OGA AAC→MKA AAC→WV AAC→AU AAC→TTA WebM→M4B FLAC→M4B MKV→M4B AVI→M4B OGG→M4B WMV→M4B Opus→M4B WMA→M4B FLV→M4B M4V→M4B MPEG→M4B 3GP→M4B AIFF→M4B AMR→M4B MPG→M4B TS→M4B MTS→M4B VOB→M4B M2TS→M4B PNG→JPG JPG→PNG PNG→WebP JPG→WebP WebP→PNG WebP→JPG HEIC→PNG HEIC→JPG MP4→MP3 PNG→JPEG JPG→JPEG JPEG→PNG JPEG→JPG PNG→PDF JPG→PDF PDF→PNG PDF→JPG HEIC→WebP MP4→WebP PDF→DOCX DOCX→PDF JPEG→WebP WebP→JPEG PNG→GIF JPG→GIF GIF→PNG GIF→JPG MP4→MOV MOV→MP4 WebP→PDF HEIC→JPEG WebP→GIF GIF→WebP HEIC→PDF MP3→WAV WAV→MP3 JPEG→PDF PDF→JPEG SVG→PNG SVG→JPG HEIC→GIF MOV→MP3 MP4→GIF GIF→MP4 JPEG→GIF GIF→JPEG PNG→AVIF JPG→AVIF AVIF→PNG AVIF→JPG MP3→M4A M4A→MP3 GIF→PDF SVG→PDF PNG→SVG JPG→SVG PDF→SVG SVG→WebP MOV→WebP MP4→WAV MP4→WebM WebM→MP4 WebP→AVIF AVIF→WebP WebP→SVG SVG→JPEG MP4→MKV MKV→MP4 HEIC→AVIF MP4→M4A JPEG→AVIF AVIF→JPEG JPEG→SVG MOV→GIF GIF→MOV WebM→MP3 AVIF→PDF MP3→FLAC FLAC→MP3 MP4→AVI AVI→MP4 MKV→MP3 GIF→AVIF AVIF→GIF SVG→GIF GIF→SVG WebM→WebP MOV→WAV XLSX→PDF CSV→PDF EPUB→PDF PDF→EPUB MOV→WebM WebM→MOV MKV→WebP PNG→ICO JPG→ICO ICO→PNG ICO→JPG MP3→AAC WAV→M4A M4A→WAV MP4→FLAC AVI→MP3 MOV→MKV MKV→MOV MOV→M4A DOCX→EPUB EPUB→DOCX CSV→DOCX PDF→TXT DOC→PDF TXT→PDF WebP→ICO ICO→WebP PPTX→PDF AVI→WebP WebM→GIF

AACM4B

Convert AAC to M4B

Free, fast and private. Your AAC files are converted right in your browser — nothing is uploaded.

Runs in your browser
No watermark
Batch & ZIP download

Need a smaller AAC? 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.

AAC vs M4B

From

AAC · Advanced Audio Coding

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

Type: Audio
Extension: .aac
MIME: audio/aac
Best for: streaming, mobile audio and video soundtracks

Lossy compression

All AAC conversions →

M4B · MPEG-4 Audiobook

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

Type: Audio
Extension: .m4b
MIME: audio/mp4
Best for: audiobooks on Apple Books and other players

Lossy compression

All M4B conversions →

Need it the other way around? Convert M4B to AAC.

AAC to M4B: frequently asked questions

Free, private and in your browser