Compress M4A
Make iPhone voice memos and M4A music files smaller with a lower AAC bitrate.
MP3, WAV, M4A, FLAC, OGG, Opus, AIFF, WMA, AMR and the sound of most videos. Files stay on your device.
How it works
- Choose your M4A files.
- Pick a lower bitrate; 64 kbps is plenty for speech.
- Click Compress and compare sizes.
- Download the smaller files.
Making M4A and AAC files smaller
M4A holds AAC audio, which sounds better than MP3 at the same bitrate, so a lower bitrate goes further. The tool decodes the file and encodes it again as AAC at the bitrate you choose: 160, 96 or 48 kbps for the High, Medium and Low presets in stereo. For a Voice Memos recording, 48 kbps mono is clear and very small.
The result is a normal M4A file that plays on iPhone, Mac, Android and in current browsers. Tags and cover art are kept unless you remove them under More options.
Staying under a size
Use Target size or Maximum size when you have a limit to meet. AAC bitrate can be set finely, so the result usually lands within a few percent of the size you ask for. When a long recording needs a very low bitrate, the tool mixes down to mono and lowers the sample rate before it lets the quality fall, and says so.
Questions
Is compressing an M4A lossy?
Yes. AAC is lossy and the file is encoded again. At 96 kbps or more the extra loss is small. Keep your original if it matters.
How do I shrink an iPhone voice memo?
Use Quality: Low, and choose Mono under More options. A voice memo then needs less than half a megabyte per minute.
Does it work on .aac and .mp4 audio files?
It accepts AAC in ADTS (.aac) files and audio in MP4 and MOV files too, and writes M4A.
Is my audio uploaded?
No. Compression runs in your browser on your device. The only downloads are the page itself and, the first time you use a format, a small encoder file from this site.