MPEG-4 audiobook .m4b
An MPEG-4 audio container commonly used for audiobooks and spoken-word recordings.
Output uses AAC. Chapters, bookmarks, cover art and DRM are not retained.
M4B file format guideM4B to OPUS converter
Convert MPEG-4 audiobook (.m4b) to OPUS for free. Choose files, review the available settings and download your results. No account needed.
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Opus .opus
An efficient audio codec suited to speech and music.
OPUS file format guideHow to convert M4B to OPUS
- Select M4B files from your device or drag them into the converter.
- Check the OPUS output. Open conversion settings if you want to make adjustments.
- Convert, compare the original and result, then download your files.
Quality, compatibility and file limits
Choose the sample rate, trim range, and mono or stereo output. Compressed audio formats can discard detail; converting to a lossless format cannot restore sound already lost. Container support depends on the codec inside the file.
Processing uses your device when possible and our servers when required. Browser files are limited to 256 MB each; server conversions to 64 MB; browser spreadsheets to 32 MB. Previews show supported content and do not guarantee identical rendering in every application.