Online M4A Compressor
Shrink M4A and AAC audio files quickly
M4A is the default audio format on Apple devices — every iPhone Voice Memo, GarageBand export, and iTunes download lands in this container with AAC encoding inside. While AAC is already more efficient than MP3 at the same bitrate, M4A files can still pile up, especially long recordings and high-quality music purchases. Our free M4A compressor re-encodes your file at a lower AAC bitrate, cutting size by up to 80% while keeping sound quality acceptable for most ears. Everything runs in your browser, so your recordings stay on your device.
Features
- Reduce M4A size by 30-80% depending on the target bitrate
- 6 quality presets: High (256 kbps) to Minimum (32 kbps)
- Custom bitrate slider for fine-grained control
- Optional mono conversion — cuts Voice Memo size in half
- Sample rate adjustment: 48 kHz, 44.1 kHz, or 22.05 kHz for speech
- Browser-based processing — no files uploaded to any server
How to Compress an M4A File
- Upload your M4A file by dragging it into the drop zone or clicking to browse
- Select a quality preset or drag the custom bitrate slider
- Optionally switch to mono or lower the sample rate under Advanced settings
- Click "Compress" and download the smaller M4A file
Frequently Asked Questions
What is the M4A format?
M4A is an audio container developed by Apple as part of the MPEG-4 standard. It typically holds AAC (Advanced Audio Coding) data, which delivers better quality than MP3 at the same bitrate. M4A is the native format for iPhone Voice Memos, iTunes/Apple Music purchases, and GarageBand exports.
Does compressing M4A reduce quality?
Yes, re-encoding at a lower bitrate is lossy — some audio detail is discarded. At 128 kbps most listeners cannot distinguish the result from the original. Below 64 kbps, artifacts become more noticeable, but the setting still works well for speech and voice recordings.
How do I compress iPhone Voice Memos?
Voice Memos are saved as M4A files. Transfer the memo to your computer (via AirDrop, iCloud, or email), then upload it here. For speech, the "Voice" preset (64 kbps mono) usually reduces the file by 70-90% with minimal quality loss.
M4A vs MP3 — which is smaller?
At the same perceived quality, M4A (AAC) produces files roughly 20% smaller than MP3. AAC is a newer, more efficient codec. However, MP3 has wider compatibility with older devices and car stereos.
What bitrate should I use for M4A?
128 kbps is transparent for most music listeners. 96 kbps is a good compromise for podcasts and audiobooks. 64 kbps works well for voice recordings and memos. 256 kbps is overkill for most purposes but preserves near-original quality.
