Combine MP3 Files into an M4B Audiobook with Chapters
Drop in your MP3s, check the order and chapter names, and get one M4B file you can play in Apple Books, on your iPhone or in your favorite audiobook app.
For the best experience, use a desktop computer.
Cover from your MP3s
Chapters
Conversion happens in this tab. Closing it will stop the process.
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How to convert MP3 to M4B
- Add your MP3 files.
Drag in the files or the whole folder. They're sorted by name automatically — 2 comes before 10.
- Check order and chapters.
Drag files to reorder, remove any you don't want, and edit chapter names. Add a title and author if you like.
- Create and download.
Click Create M4B and download one audiobook file with chapters.
Made for audiobooks, not just audio files
Chapters made for you
Each MP3 becomes a chapter. We tidy up messy file names, and you can rename any chapter.
Plays where audiobooks belong
Works with Apple Books, iPhone, Audiobookshelf, VLC and other M4B players, with chapters and cover.
Private by design
Your files are processed on your computer and never uploaded.
No install, no command line
No need for m4b-tool, Docker or desktop apps that won't open. It just works in your browser.
Frequently asked questions
How do I combine MP3 files into an M4B audiobook?
Add all the MP3 files of the book, check that they're in the right order, then click Create M4B. You'll get a single M4B file with one chapter per MP3.
How are the files ordered?
By file name, in natural order (so "2" comes before "10"). You can drag files to change the order before converting.
Where do the chapter names come from?
From your file names. We remove clutter like "_64kb" and repeated prefixes, so "mybook_01_64kb.mp3" becomes "Chapter 01". You can rename any chapter, or switch back to the original file names.
Will the M4B work in Apple Books and on iPhone?
Yes. The M4B is marked as an audiobook and includes chapters, so Apple Books and most audiobook apps show the chapter list. On iPhone, open the file from the Files app to play it, or add it to Books on your Mac and sync it to your iPhone.
Does it keep the cover art?
If your MP3 files have a cover image, it's added to the M4B automatically. Adding or changing a cover is a Pro feature.
Is there a limit on the number of files or length?
You can add up to 500 MP3 files per book, with no length limit. Very large books (over 1 GB) take longer and may fail on computers with little memory.
Are my MP3 files uploaded?
No. Everything is processed in your browser on your own computer.