M4B and MP3 Tag Editor for Audiobooks: metadata and cover

Where it runs

Works in a current Chrome, Edge, Firefox or Safari, on Windows, Mac, Linux and Chromebook computers, Android phones, iPhones and iPads. Nothing to install, no account.

The first file loads the audio engine (ffmpeg, about 31 MB) once, and your browser keeps it. Very long books are easiest on a computer, which has more memory than a phone.

4 simple steps.

Drop your audiobook

One M4B, M4A or MP3, or a whole folder of MP3s for one book. Its tags appear at once.

Edit the details

Title, author, narrator, series and book number, year, genre, copyright and description.

Set the cover

Click, drop or paste an image. It is cropped to a square, up to 2400×2400.

Save

The audio and chapters are copied untouched with the new tags. Folders download as a ZIP.

Which tags audiobook apps read

Audiobook players build their library from the tags inside each file. Getting them right means the book shows its proper title and cover, sorts under the right author, and sits in its series in the right place.

Field	M4B / M4A	MP3
Title	Title and album	Title and album (a folder keeps each file’s title)
Author	Artist and album artist	Artist and album artist
Narrator	Composer	Composer
Series, book number	Show, episode	“series”, “series-part”
Description	Description, long description, comment	Description, comment
Cover	Embedded cover art	Embedded picture (APIC)

Cover art that looks right everywhere

Use a square image. Stores and players crop or letterbox anything else.
2400×2400 pixels is what ACX and most retailers ask for; anything over 1400 looks sharp in apps.
JPEG keeps the file small. Very large PNGs are re-encoded as high-quality JPEG.

Need to fix chapters too? The chapter editor works the same way, without re-encoding.

Questions, answered.

How do I change the cover of an M4B audiobook?

Drop the M4B here, then click the cover, drop an image on it, or paste one from your clipboard. The image is cropped to a square (up to 2400×2400) and embedded when you press Save. Nothing else in the file changes.

Does editing tags re-encode the audio?

No. The audio is copied exactly as it is, along with the chapters, so there is no quality loss and saving takes seconds even for a long book.

Where are series and book number saved?

In M4B and M4A files they are written as the show and episode tags, and in MP3 files as “series” and “series-part” tags. Audiobookshelf reads both, so the book lands in the right series.

Can I tag a whole folder of MP3s at once?

Yes. Drop the folder, and the book details you enter go on every file, while each file keeps its own chapter title. Tick “Number the files” to set track numbers in order. All the files download together as a ZIP.

Why does Apple Books file my M4B under music?

Apple apps use a “media kind” tag to tell books from music. Saving here marks M4B and M4A files as audiobooks, so they appear under Books.

Is my audiobook uploaded?

No. Everything happens inside your browser and the file never leaves your device.