One file, every chapter
The whole book lives in a single file with a chapter marker for each chapter of the EPUB. No folder of 40 MP3s to keep in order.
EPUB to M4B
Convert EPUB to M4B
Drop in your EPUB and get back one M4B audiobook: narrated by a studio voice, with every chapter marked, the cover embedded and the book details filled in.
Drop your EPUB here
or · up to 100 MB
book.epub
2.1 MB · Ready to narrate
Reading your file…
DRM-free EPUB 2 and 3. Prefer MP3? Every book also exports as MP3 or WAV.
Why M4B is the right format
Looks right in your library
Cover, title, author, narrator, series, publisher, year and description are written into the file, so Apple Books, Plex and Audiobookshelf show it properly. Review them before you export.
Small and remembers your place
AAC at 64 kbps keeps an hour of narration around 30 MB, and M4B players pick up where you left off.
How it works
Three steps from a file on your desktop to an audiobook in your library.
1
Upload your EPUB
Drag it into the composer above. Chapters, cover and metadata are read from the file on the spot.
2
Pick a language and a voice
47 languages and 30 studio voices, or a different voice for each character. Fix any line in the studio before you export.
3
Export as M4B
Choose M4B, review the book details, and export. Warblize narrates the book, masters it to audiobook loudness and hands you one chaptered file.
Skip the m4b-tool pipeline
Ebook to M4B the DIY way means three tools and a robotic voice. This is one upload.
Calibre + TTS + m4b-tool
- Convert, synthesise, then merge: three tools to install
- Chapter markers rebuilt by hand or lost
- Cover and tags added separately, if at all
- One flat text-to-speech voice
- Loudness that jumps from chapter to chapter
Warblize
- Upload the EPUB, download the M4B
- Chapter markers straight from the EPUB
- Cover, author, narrator and series embedded
- Studio voices, with a cast per book
- Every chapter mastered to the same loudness
The easiest way to convert EPUB to M4B
M4B is the audiobook format: an AAC audio file with chapter markers, cover art and book metadata built in. Getting there from an EPUB usually means converting the ebook to text, running it through a text-to-speech engine, and stitching the result together with m4b-tool or FFmpeg. Warblize does all of it from a single upload.
The EPUB parser reads the book's navigation document, so every chapter in the table of contents becomes a chapter marker in the M4B. The cover image becomes the file's artwork, and the title and author are carried over. Footnotes, italics and image captions are handled before narration, so the voice reads the book, not the markup.
Each chapter is mastered to audiobook loudness specs and encoded to AAC, then joined into one file you can drop into Apple Books, Plex, Audiobookshelf, BookPlayer or Smart AudioBook Player. Need MP3 for an older device or WAV for a publisher? The same book exports in those formats too.
How to create an M4B audiobookEPUB to M4B, answered
What is an M4B file?
M4B is the standard audiobook format: AAC audio in an MP4 container, with chapter markers, cover art and metadata inside the file. Apple Books, Plex, Audiobookshelf and most audiobook apps play it and remember your position.
Are the EPUB's chapters kept as chapter markers?
Yes. Warblize reads the EPUB's table of contents and creates one chapter per chapter of the book. Each one gets a marker in the M4B with its title, so you can skip between them in any player.
Is the cover embedded?
Yes. The book's cover is cropped to a square, the shape audiobook apps use, and written into the M4B as its artwork, along with the title, author, narrator, series, publisher, year and description. Details found in the EPUB are filled in for you, and you can review or add any of them before exporting. Only the title is required.
Does it work with DRM-protected EPUBs?
No. Warblize converts DRM-free EPUBs that you own or have the rights to. EPUB 2 and EPUB 3 are both supported.
How big is the M4B file?
Narration is encoded as AAC at 64 kbps, which comes to about 30 MB per hour of audio. A 10-hour novel is roughly 300 MB.
Can I export a single chapter as M4B?
Yes. Pick "Current chapter" in the export menu to get that chapter on its own as an M4B, or "Full project" for the whole book in one file.
How much does it cost?
Uploading and looking through your book is free. Narration is credit-based: one credit covers 60 minutes of finished audio, and credits stay valid for 12 months. Exporting as M4B costs nothing extra.
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