M4B is Apple's audiobook format supporting bookmarks.
Drag & drop files here
PDF, DOCX, JPG, PNG, MP4, MP3, and 200+ formats
ConvertFly is your universal app for file conversions. We support nearly all audio, video, document, ebook, archive, image, spreadsheet, and presentation formats. Plus, you can use our online tool without downloading any software.
ConvertFly has been trusted by our users and customers since its founding in 2026. Your files are encrypted during transfer and automatically deleted after 24 hours. Read more about data security at ConvertFly. We have accomplished Privacy Shield certification.
Powered by industry-standard open source engines including FFmpeg, LibreOffice, and Sharp. Most conversion types can be adjusted to your needs such as setting the quality and many other options.
Our REST API allows custom integrations with your app. You pay only for what you use with credit-based pricing, and there are volume discounts for heavy users. Check out the ConvertFly API.
Convert M4B files to 13+ formats online for free. Fast, secure audio conversion. No signup, no install. Swiss-hosted, files auto-delete after 24h.