Extract Audio from MP4 to M4A — Free Online Tool
Extract the audio track from an MP4 video and save it as an M4A file — preserving the original AAC audio stream without re-encoding, so there's zero quality loss. M4A is the standard audio-only MPEG-4 container used by Apple iTunes, Music, and Podcasts, making this the ideal format for extracted audio you plan to use on Apple devices or distribute as podcast content.
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FFmpeg Command
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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:
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DownloadHow It Works
MP4 files typically store their audio as AAC (Advanced Audio Coding), and M4A is simply an MPEG-4 container restricted to audio-only content — also defaulting to AAC. Because both formats share the same underlying codec, this conversion is primarily a remux: the AAC audio stream is lifted out of the MP4 container and placed into the M4A container without any decoding or re-encoding. The video stream is explicitly discarded using the -vn flag. The result is that no audio quality is lost — the bitrate, sample rate, and channel layout remain exactly as they were in the source MP4. Chapter markers embedded in the MP4 are also preserved in the output M4A, since both containers support chapters.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool. In this browser-based tool, FFmpeg runs locally via WebAssembly (FFmpeg.wasm) — your MP4 file never leaves your device. |
-i input.mp4
|
Specifies the input file — your source MP4 video. FFmpeg reads the container and identifies all streams inside, which for a typical MP4 will include at least one H.264 video stream and one AAC audio stream. |
-vn
|
Stands for 'video none' — instructs FFmpeg to discard all video streams from the input. This is what transforms the conversion from a full MP4 copy into an audio-only extraction, and is essential since M4A is an audio-only container. |
-c:a aac
|
Sets the audio codec to AAC for the output. Since the source MP4 almost certainly already contains AAC audio, FFmpeg will stream-copy the existing AAC data into the M4A container without re-encoding, preserving the original quality and bitrate. |
-b:a 128k
|
Sets the target audio bitrate to 128 kilobits per second. This only takes effect if a re-encode is actually performed; if the audio is stream-copied from an existing AAC track, the original bitrate is preserved regardless of this value. |
-vn
|
A second instance of the video-disable flag, applied on the output side as a safeguard. While redundant when the first -vn is already present, it reinforces that no video data should appear in the output M4A file. |
output.m4a
|
The output filename with the .m4a extension. FFmpeg uses this extension to automatically select the MPEG-4 audio container format, which is structurally similar to MP4 but signals to Apple devices and media players that the file contains audio only. |
Common Use Cases
- Extracting a conference talk or lecture recording from MP4 to listen to offline on an iPhone or Apple Watch via the Music or Podcasts app
- Pulling the AAC audio from a screen recording to use as a voiceover track in a podcast episode, without the overhead of carrying unused video data
- Stripping audio from purchased or downloaded MP4 music videos to create an iTunes-compatible M4A file that syncs cleanly with Apple Music library
- Reducing file size for archiving by discarding the video stream from interview recordings where only the spoken audio matters
- Preparing an audio-only feed from MP4 video content for distribution to podcast platforms that accept M4A with iTunes metadata
- Extracting chapter-marked audio from a multi-section MP4 course video so chapter navigation is retained in compatible podcast players
Frequently Asked Questions
No — not with this specific conversion. Because MP4 files almost always contain AAC audio, and M4A is also an AAC container, the audio stream is copied directly from one container to the other without re-encoding. The FFmpeg command uses -c:a aac, which in this context copies the existing AAC stream rather than transcoding it, meaning the bitrate and quality are identical to the source. Quality loss only occurs when audio is decoded and then re-encoded into a different format.
The dramatic size reduction comes entirely from discarding the video stream, not from any audio compression. In a typical MP4, the video track accounts for 80–95% of the file size. The -vn flag instructs FFmpeg to drop all video streams, so the M4A contains only the audio data. If your original MP4 was 500MB, the resulting M4A might be 20–40MB depending on the audio bitrate and duration — the audio quality itself is unchanged.
Yes. Both MP4 and M4A support chapter metadata, and FFmpeg carries chapter data through the remux by default. This is particularly useful for long-form content like courses, audiobooks, or recorded webinars where chapter navigation is important. Note that subtitle tracks and additional audio tracks from the MP4 are not carried into M4A, since the format only supports a single audio stream and has no subtitle support.
M4A with AAC audio is natively supported by all Apple platforms including iTunes, Apple Music, Podcasts, and QuickTime, as well as most modern podcast hosting platforms. Spotify does not accept M4A uploads from artists — it requires MP3 or OGG for submissions via Spotify for Artists. For maximum platform compatibility across streaming services, MP3 is a safer choice, but for Apple-ecosystem use and podcast RSS feeds, M4A is widely accepted and preferred.
Replace the value after -b:a in the command. For example, to extract at 192kbps instead of the default 128kbps, run: ffmpeg -i input.mp4 -vn -c:a aac -b:a 192k -vn output.m4a. However, keep in mind that if the source MP4 audio is already encoded at 128kbps, increasing the -b:a value will trigger a re-encode at a higher bitrate without recovering quality that was already lost — it will only increase file size. Matching or going below the source bitrate is generally the better practice.
By default, FFmpeg selects the first audio stream (stream index 0:a:0) when the output container supports only one audio track, which is the case for M4A. If your MP4 has multiple audio tracks — such as different languages or a commentary track — only the default audio stream will be extracted. To select a specific track, add -map 0:a:1 (for the second audio track) to the command before the output filename: ffmpeg -i input.mp4 -vn -map 0:a:1 -c:a aac -b:a 128k output.m4a.
Technical Notes
M4A uses the same MPEG-4 Part 14 container structure as MP4 but is identified by the .m4a extension and an audio-only brand in the file header (M4A or mp42), signaling to players that no video stream should be expected. Because both formats share the AAC codec by default, this conversion avoids the generational quality loss that would occur if transcoding to MP3 or OGG. The -vn flag appears twice in the resolved command — once is sufficient functionally, but it is harmless. M4A supports iTunes-specific metadata atoms (iTunSMPB for gapless playback, iTunes rating and grouping fields) which may or may not be present depending on whether the source MP4 carried them. Embedded album art stored as a video stream in the MP4 will be dropped along with the video; art stored as a metadata attachment should be preserved. M4A does not support subtitle tracks or multiple simultaneous audio streams, so any secondary audio streams and subtitle tracks present in the source MP4 are silently discarded. For files over 1GB — such as long uncompressed screen recordings — the FFmpeg command displayed on this page can be run locally on the desktop without any file size restrictions.