M4B editor: chapters, tags & cover
Edit an M4B file right in your browser: rename, add, remove, or re-time chapters, fix the tags, and change the cover, without re-encoding the audio. Your files never leave your device.
Drop an M4B to edit, or click to browse
M4B · M4A · one file · edits are saved without re-encoding
How M4B editing works
Drop a finished M4B and the tool reads its chapters, tags, and cover. Adjust anything — chapter titles and times, the book metadata, the cover — then save. Because only the markers and metadata change, the audio is copied rather than re-encoded, so there is no quality loss and the save is fast. Everything runs locally through a WebAssembly build of FFmpeg; nothing is uploaded.
Editing M4B: common questions
- Can I add chapters to an M4B that has none?
- Yes. Drop the file, then use "Add chapter" to place markers at the times you want, each with its own title. It also works the other way — you can remove or re-time existing chapters.
- Does editing re-encode the audio?
- No. Only the chapter markers, tags, and cover change; the audio stream is copied through untouched. That means no quality loss and a near-instant save, even for a long book.
- What can I edit?
- Chapter titles and start times (add, remove, rename, re-time), the book title, author, narrator, year, and genre, and the cover image (keep, replace, or remove).
- How do I change the cover of an M4B?
- Drop the M4B, then click "Replace image" under Cover (or "Add cover" if it has none) and pick a JPG or PNG. It's fitted to 1200×1200 and embedded when you save. "Remove cover" takes it out.
- Are my files uploaded anywhere?
- No. Editing runs entirely inside your browser using a WebAssembly build of FFmpeg. Your audiobook never leaves your device. Open your browser's Network tab while saving to verify there are no uploads.
- How do I enter chapter times?
- As H:MM:SS measured from the start of the book (for example 1:23:45), or plain seconds. The first chapter must start at 0:00:00, and times must increase and stay within the book length.