AIFF to M4B Converter

Turn an AIFF Recording Into an M4B Audiobook

This tutorial is for anyone with a long AIFF file — a narrated book, a lecture, a sermon, hours of voice notes — who wants a player that remembers where they stopped. Converting to M4B re-encodes your audio to AAC inside Apple's audiobook container, so apps like Apple Books file it as an audiobook and resume from your last position instead of restarting at zero.

How to Convert AIFF to M4B

1. Upload Your AIFF File: Drag and drop your .aiff or .aif file onto the page, or click "Add Files" to browse. You can queue several at once, and each is converted with the same settings.
2. Set the Quality Preset: Under Advanced Options, leave Quality Preset on its default for a clean result, or switch to Constant Bitrate / Custom Bitrate to set an exact kbps for the AAC output — lower bitrates keep a multi-hour book small.
3. Adjust Audio (Optional): Use Audio Channel to fold a stereo recording to mono, Audio Sample Rate to downsample speech, or Trim to keep only part of the file.
4. Convert and Download: Click Convert and save your .m4b. No sign-up, no watermark.

Walk-through: Picking the Right Bitrate for Spoken Word

AIFF is uncompressed PCM, so it stores about 10 MB of data per minute of CD-quality stereo — a one-hour recording is roughly 600 MB. M4B re-encodes that to AAC, which is where almost all the size savings come from. Because this is a lossless-to-lossy step (AAC permanently discards detail to shrink the file), the bitrate you pick is the main lever between size and fidelity. The good news for audiobooks: speech needs far less bitrate than music, so a modest setting still sounds clear while keeping a long book manageable.

• Plain narration, want it small: a low-to-medium Quality Preset, or Constant Bitrate around 64 kbps mono, keeps a multi-hour book compact.
• Narration with some music or sound design: step up the Constant Bitrate (96-128 kbps) so the non-speech parts stay clean.
• Mostly music or wide dynamic range: use a higher preset or 192 kbps and up — the lossy trade matters more when the content isn't just voice.
• Fold stereo speech to mono: if the recording is one voice, set Audio Channel to mono to roughly halve the data the encoder has to spend.

Common Errors and How to Fix Them

• "The file is huge even after converting" — You likely picked a music-grade bitrate for a voice recording. Spoken word is fine at low bitrates; drop the Constant Bitrate and, for a single voice, fold to mono.
• "My player restarts instead of resuming" — The resume behavior comes from the player honoring the .m4b extension. Use Apple Books, VLC, or a dedicated audiobook app; a generic music player may treat it as a track and restart.
• "It won't play on my Android phone" — M4B plays natively on iOS and macOS. On Android, install a third-party audiobook player that supports M4B, since the stock player may not.
• "I expected named chapters and there aren't any" — This converter outputs a single M4B audio file and does not author chapter markers (see the FAQ below for what to do instead).
• "The audio sounds worse than the AIFF" — That is the lossy AAC step. Re-convert from the original AIFF at a higher bitrate; never re-encode from an already-compressed copy.

When This Doesn't Work

This page makes one resumable M4B from one source file using audio controls only — Quality Preset, bitrate, channels, sample rate, and trim. It does not stitch many files into one book, author named chapter markers, or add cover art, so it is not a full audiobook-production tool. If you need a chaptered book built from multiple parts, a dedicated audiobook-builder application is the right tool for that part. If you only want a small, universally playable file rather than the audiobook behavior, convert to MP3 instead, or to M4A for the same AAC audio without the audiobook flag. To keep a smaller copy with no quality loss at all, convert to lossless FLAC.

Frequently Asked Questions

Does this converter add chapter markers to the M4B?

No. It produces a single M4B audio file and exposes audio controls — Quality Preset, bitrate, Audio Channel, Audio Sample Rate, and Trim — but it does not author named chapters or merge multiple files into a chaptered book. You still get the core M4B benefit: because the output carries the .m4b extension, compatible players file it as an audiobook and remember your position. If you specifically need named chapters or to stitch several files into one book, use a dedicated audiobook-builder application for that step.

Will I lose quality converting AIFF to M4B?

Some, by design. AIFF is uncompressed PCM (lossless), and M4B stores AAC, which is lossy — this converter re-encodes your audio rather than copying it, permanently discarding detail to shrink the file. For spoken word that is rarely noticeable, and the trade is worth it because you gain resume/bookmark behavior plus a much smaller file. Keep the original AIFF if it is your only master or you plan further edits.

Why does an M4B remember my place when a plain audio file doesn't?

It is the format's role, not magic. Apple defined M4B as an audiobook container, so players like Apple Books recognize the .m4b extension and treat the file as an audiobook — saving your last position and resuming there next time. A plain audio file is usually treated as a music track and restarts from the beginning. Converting to M4B is what flips that behavior on.

What bitrate should I pick for a multi-hour AIFF narration?

Speech needs far less bitrate than music. In our testing, a single-voice narration re-encoded to AAC stayed clear at modest bitrates, and the lower bitrate kept a multi-hour book reasonably small. Pick a Quality Preset for a quick result, or use Constant Bitrate to set an exact kbps — for one voice, folding to mono with Audio Channel saves more space again. Reach for higher bitrates only when the source has music or wide dynamic range.

Can I play the M4B on Android or Windows?

Yes, with the right app. M4B plays natively on iOS and macOS. On Windows you can use VLC or iTunes; on Android you will typically need a third-party audiobook player that supports M4B, since stock players may not. If you need a file that plays on nearly anything, including older car stereos, MP3 is the safer choice.

Is the conversion private, and how long is my file kept?

Your AIFF is uploaded over an encrypted (TLS) connection, converted on our servers, and the M4B is returned to you. Files are deleted automatically a few hours after conversion — no sign-up, no watermark, and nothing is shared or made public. To go the other direction later, convert M4B back to AIFF with the same workflow.