M4B – MPEG-4 Audiobook
M4B is an MPEG-4 audio file for audiobooks. It supports chapters and remembers where you stopped listening.
More M4B conversionsDrop your M4B files here
or click to choose M4B files · up to 95MB each
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Audio
Frequently asked questions
Is it really free?
Yes. There is no sign-up and no watermark. To keep the service available for everyone there is a 95MB limit per file and a cap on how many files one connection can process in a short period.
Are my files stored?
Your upload is used only to make the converted file. Images are processed in memory; other files are written to a private temporary folder that is deleted as soon as the conversion finishes. Nothing is kept after the result has been sent back.
Will quality drop?
For images, a little, by design: the image is re-encoded at the Quality you choose (default 75%). Audio and video are re-encoded with high-quality settings; documents keep their text and layout as far as the target format allows. Converting never restores detail that is already missing from the original.
How this works: your file is uploaded over HTTPS and converted on this server with open-source engines (libvips for images, FFmpeg for audio and video, LibreOffice and Pandoc for documents, Calibre for ebooks, Ghostscript and Inkscape for PDF and vector files). Images are processed in memory; other files use a private temporary folder that is deleted as soon as the conversion finishes.