Convert MOV to M4B — Free Online Tool
Convert MOV video files to M4B audiobook format by stripping the video stream and encoding the audio track to AAC, producing a chapter-aware audiobook file compatible with Apple Books, iTunes, and podcast apps. This tool runs entirely in your browser — no uploads, no server, no waiting.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your MOV file here
or click to browse
Free — no uploads, no signups. Your files never leave your browser.
Settings
Note: Browser-based encoding uses approximate quality targets. For precise CRF compression, copy the FFmpeg command above and run it on your desktop.
Estimated output:
Conversion Complete!
DownloadHow It Works
MOV is a video container that typically carries both video and audio streams. When converting to M4B, the video stream is discarded entirely — M4B is a pure audio format derived from the MPEG-4 container, designed specifically for audiobooks and long-form spoken content. The audio stream from the MOV file is re-encoded to AAC at 128k bitrate, which is the standard codec for M4B files and is natively supported by Apple Books, QuickTime, and most podcast players. If the MOV source already contains an AAC audio track, the re-encoding step slightly degrades quality (generation loss), but at 128k the result is indistinguishable for speech content. The output file uses the -movflags +faststart flag to move the MOOV atom to the beginning of the file, enabling progressive playback and faster loading in audiobook apps. Chapter markers from the MOV source are preserved in the M4B output, since both containers support the MPEG-4 chapter format.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg program, the open-source multimedia processing engine that powers this conversion both in the browser (via FFmpeg.wasm) and on the desktop command line. |
-i input.mov
|
Specifies the input file — in this case a MOV (QuickTime) container, which may contain video, audio, chapter tracks, and metadata. FFmpeg reads all available streams from this file before applying output options. |
-c:a aac
|
Sets the audio codec for the output to AAC (Advanced Audio Coding), the only codec natively supported in M4B files and required by Apple Books and most audiobook platforms. Any audio stream in the MOV file — whether it was AAC, PCM, or another codec — is re-encoded to AAC. |
-b:a 128k
|
Sets the audio bitrate to 128 kilobits per second, the standard bitrate for M4B audiobooks. At this bitrate, AAC produces clear, intelligible speech audio at a file size of roughly 57MB per hour — a practical balance for audiobook distribution. |
-movflags +faststart
|
Moves the MOOV metadata atom to the beginning of the M4B file after encoding is complete. This allows audiobook apps and podcast players to begin playback immediately without downloading the entire file, which is essential for streaming large M4B audiobooks. |
output.m4b
|
Defines the output filename with the .m4b extension, which signals to Apple Books, iTunes, and compatible podcast apps that this MPEG-4 audio file should be treated as an audiobook with bookmarking and chapter navigation enabled. |
Common Use Cases
- Convert a recorded lecture or presentation (saved as MOV from QuickTime or Zoom) into an M4B audiobook so listeners can resume playback at the exact point they left off using bookmarking
- Package a multi-chapter audio drama or podcast series recorded in MOV format into a single M4B file with embedded chapter markers, playable natively in Apple Books without a separate RSS feed
- Turn a screencasted tutorial or course video into an M4B listening experience for commuters who want to absorb the audio content without watching the screen
- Convert a MOV voice memo or interview recording into M4B format for distribution as an audiobook on platforms like Findaway Voices or Authors Republic that require MPEG-4 audio containers
- Extract narration audio from a MOV video produced in Final Cut Pro and deliver it as an M4B file to listeners who purchased an audio-only version of a video course
Frequently Asked Questions
Yes, in most cases. Both MOV and M4B use the MPEG-4 container's chapter track format, so chapter metadata is typically preserved during this conversion without any extra flags. However, chapter compatibility depends on how they were authored — chapters created in Final Cut Pro or QuickTime Player are the most reliably transferred. If your chapters don't appear in Apple Books after conversion, you may need to use a tool like mp4chaps to re-embed them as text chapter markers in the M4B file.
Yes, there is some quality loss because this conversion re-encodes the audio to AAC at 128k bitrate, even if the original MOV file already contained AAC audio. This is called generation loss. For speech and narration content — the primary use case for M4B — the difference is essentially inaudible at 128k. If your source contains high-fidelity music or you need archival quality, consider raising the bitrate to 192k or 256k by modifying the -b:a flag in the FFmpeg command.
No, this is correct and expected behavior. M4B is a purely audio format; it does not support video streams by specification. The conversion intentionally discards all video data from the MOV source and retains only the audio. If you need to keep the video, you should convert to MP4 or MKV instead. M4B files are designed for audiobook and podcast playback, where video is irrelevant.
Replace the -b:a 128k value with a higher bitrate such as -b:a 192k or -b:a 256k. For example: ffmpeg -i input.mov -c:a aac -b:a 256k -movflags +faststart output.m4b. Higher bitrates produce larger files but preserve more audio detail, which matters if your MOV source contains music, sound design, or studio-quality narration. The maximum practical bitrate for AAC in M4B files is 320k, though most audiobook platforms accept and display files up to 256k.
Yes, on macOS or Linux you can use a shell loop: for f in *.mov; do ffmpeg -i "$f" -c:a aac -b:a 128k -movflags +faststart "${f%.mov}.m4b"; done. On Windows Command Prompt, use: for %f in (*.mov) do ffmpeg -i "%f" -c:a aac -b:a 128k -movflags +faststart "%~nf.m4b". This is especially useful if you've split a long recording into chapter-length MOV files and want to convert them all in one pass before joining them into a single M4B.
Yes. Apple Books and iTunes identify M4B files by their file extension and the AAC audio codec inside the MPEG-4 container — both of which this conversion produces correctly. The -movflags +faststart flag also ensures the file loads quickly without buffering. To appear in your Apple Books library, simply drag the M4B file into the Books app or sync it via Finder. Metadata like title, author, and cover art can be added separately using a tag editor such as Mp3tag or AtomicParrot before importing.
Technical Notes
M4B is structurally identical to M4A (and very similar to MP4) but uses the .m4b extension as a signal to media players that the file should be treated as an audiobook, enabling bookmarking and chapter navigation. The AAC codec used in this conversion is a lossy codec standardized under MPEG-4 Part 3; it delivers better audio quality than MP3 at equivalent bitrates, making 128k AAC suitable for spoken-word content where MP3 would require at least 160k for comparable clarity. One important limitation: M4B does not support multiple audio tracks — if your MOV source has several audio tracks (e.g., separate language dubs or a stereo plus surround mix), only the first audio track is encoded into the output. Subtitle streams are also dropped, as M4B has no subtitle support. The MOOV atom relocation via -movflags +faststart is critical for audiobook use because it allows apps to begin playback before the entire file is downloaded, which matters for large files distributed over the internet. If you plan to distribute the M4B file publicly, embed ID3-compatible metadata (title, artist, album, cover art) using a tag editor after conversion, as FFmpeg does not automatically transfer all metadata fields from MOV to M4B.