Convert M4B to OPUS
Convert your M4B audio files to OPUS directly in your browser.
How to convert audio in 3 steps
Choose a M4B audio file.
Click convert to OPUS.
Download your OPUS audio.
Format descriptions
M4B — M4B is the MP4-based container used for audiobooks. It supports chapters and bookmarks, using the AAC codec just like M4A.
OPUS — OPUS is a modern, open and royalty-free audio codec. It delivers excellent quality even at low bitrates, making it ideal for streaming, voice and podcasts.
Technical comparison: M4B vs OPUS
Technical breakdown of the M4B and OPUS specifications: compression, colour, transparency and animation support.
| Property | M4B | Opus |
|---|---|---|
| Specification | M4B (MPEG-4 Audiobook Container) | Opus (Opus Interactive Audio Codec) |
| Media type | Audio | Audio |
| Compression | Lossy · AAC | Lossy · Opus (RFC 6716) |
| Color space / bit depth | 16-bit up to 48 kHz | 16-bit, 8-48 kHz |
| Transparency | Not applicable | Not applicable |
| Animation | No (static) | No (static) |
| Best for | M4B is the MP4-based container used for audiobooks. It supports chapters and bookmarks, using the AAC codec just like M4A. | OPUS is a modern, open and royalty-free audio codec. It delivers excellent quality even at low bitrates, making it ideal for streaming, voice and podcasts. |
What happens when converting M4B to OPUS?
The M4B data is decoded inside your browser with WebAssembly and re-encoded to the OPUS specification, so no file is ever uploaded to a server. OPUS uses lossy compression: the file gets far lighter, but a small amount of fine detail is discarded in the process.
Frequently Asked Questions
What is audio conversion?
Audio conversion changes an audio file from one format to another, for example from M4B to OPUS, while keeping the audio content.
Are my audio files uploaded?
No. This tool processes audio files directly in your browser. Your audio files are never sent to a server.
Which audio formats are supported?
This tool converts M4B audio files to OPUS, all in your browser.
Is it really free and unlimited?
Yes, the tool is completely free and you can convert as many audio files as you want, with no limits.
Does it work on mobile too?
Yes, it works on any modern device, including smartphones, tablets and desktop computers.
Which format will the result be in?
The converted file will always be in OPUS format, ready to download and use.
About the audio converter
Convert M4B to OPUS audio online for free. Everything happens in your browser: your files are never uploaded to a server, and you need no downloads or sign-up to get started.
See also:
- Audio Converters
- Compress Audio OnlineCompress MP3, WAV, OGG, M4A, AAC, OGA, FLAC, ALAC, AIFF, OPUS, M4B and AC3 audio files online for free. Reduce the file size of your audio recordings while keeping good quality. Everything happens in your browser: audio files are never uploaded to a server, and you need no downloads or sign-up to get started.
- Convert M4B to MP3Convert M4B to MP3 audio online for free. Everything happens in your browser: your files are never uploaded to a server, and you need no downloads or sign-up to get started.
- Convert M4B to WAVConvert M4B to WAV audio online for free. Everything happens in your browser: your files are never uploaded to a server, and you need no downloads or sign-up to get started.
- Convert M4B to OGGConvert M4B to OGG audio online for free. Everything happens in your browser: your files are never uploaded to a server, and you need no downloads or sign-up to get started.