Files to Merge
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This tool is for the opposite job of splitting an audiobook: combining a folder of separate MP3 files — ripped chapters, podcast episodes, or library downloads — into a single M4B audiobook with proper chapter markers. Each MP3 you add becomes one chapter in the output, in whatever order you arrange them.
This matters because a folder of forty individual MP3 tracks plays poorly in most audiobook apps: no chapter navigation, no resume position synced across the set, and no way to jump forward ten chapters without scrubbing through files one at a time. Merging into M4B fixes all of that in one step.
Drag the whole folder of MP3 files into the drop zone, or click to browse and select them. They'll appear in the tracks table on the right, where you can drag to reorder them — this order becomes the chapter order in the final M4B.
Set a title, author, and cover art so the audiobook displays correctly once imported. Album, year, genre, and a comment field are also available if you want the file fully tagged — useful if you're building out a personal audiobook library with consistent metadata.
Choose the output bitrate from the Quality dropdown. For spoken-word content, 64–96 kbps AAC keeps file size reasonable without a noticeable quality drop — audiobooks don't need music-grade bitrates.
The tool merges every track into a single M4B file with one chapter per MP3, embeds your metadata and cover art, and downloads the result directly to your device. The whole process runs locally — no file is ever uploaded.
Yes. Every MP3 you add becomes a single chapter in the resulting M4B, in the order you arrange them in the tracks table. Chapter titles default to the source filenames and can be renamed before converting.
Yes — drop an image into the cover art zone in the Metadata panel before converting. JPEG, PNG, and WebP are all supported. The cover is embedded directly in the M4B file and will display in Apple Books, Audiobookshelf, and other M4B-compatible apps.
Yes. Drag and drop the files within the tracks table to set the playback order. Get this right before converting — the resulting M4B plays chapters in exactly the order you set, and reordering afterward would mean starting over.
Title, artist or author, album, year, genre, comment, and cover art. None of these are required — leave them blank and the tool will use sensible defaults — but filling them in makes the file display properly in audiobook library apps.
We don't impose one. The practical limit is your device's memory. For large batches — fifty-plus files or several gigabytes total — enable Low-RAM mode, which streams data to disk instead of holding everything in memory at once.
No. Every file is read and merged locally in your browser using WebAssembly. Nothing is sent to a server — your audiobook is built entirely on your own device.