How to Compress AAC Files on MacSave 40-60% storage space without losing quality
What Is AAC (Advanced Audio Coding)?
AAC is a lossy audio codec designed as the successor to MP3, offering better audio quality at the same bitrate. AAC is the default audio format for Apple Music, iTunes, YouTube, and most streaming platforms. It is part of the MPEG-4 standard and provides superior compression efficiency.
Why Are AAC Files So Large?
AAC files are large when encoded at high bitrates (256-320 kbps) which Apple Music and iTunes use by default. An average AAC music library contains thousands of songs, each at 7-10MB, adding up to 30-80GB. Audiobooks and long podcasts in AAC format can also consume significant space.
Typical AAC Compression Results
Before
3-10MB per song (128-256 kbps)
After
1.5-5MB per song
40-60%
Smaller
Compression Ratio
1.5:1 to 2.5:1
Codecs
AAC-LC, HE-AAC (v1/v2), AAC-ELD
How to Compress AAC Files on Mac (Step by Step)
Follow these steps to compress your AAC files using MediaOptim on macOS:
Open MediaOptim
Launch MediaOptim. It handles AAC files with Apple's native Core Audio framework for best quality.
Add AAC files
Drag your AAC music or podcast files into the app.
Set target bitrate
Choose "Music" (128 kbps VBR) or "Podcast" (96 kbps VBR) for optimal size-quality balance.
Compress
MediaOptim re-encodes AAC files using Apple's built-in encoder for best compatibility.
Compare
Listen to before and after. At recommended settings, the quality difference is inaudible.
AAC Technical Details & Compression Tips
Best Quality Settings
128 kbps AAC is transparent for most listeners (equivalent to MP3 192 kbps). 96 kbps is excellent for podcasts and voice. VBR mode allows the encoder to allocate more bits to complex passages.
When to Convert vs Compress
AAC is already an efficient modern format. Reduce bitrate rather than converting. For maximum efficiency, Opus codec at 96-128 kbps matches AAC 192-256 kbps quality.
Technical Specifications
- Part of MPEG-4 standard, successor to MP3
- 20-30% more efficient than MP3 at same bitrate
- Supports sample rates up to 96 kHz
- Apple's preferred codec (iTunes, Apple Music, iPhone)
- HE-AAC variant designed for low bitrates (streaming)
Frequently Asked Questions
How do I compress AAC files on Mac?
Use MediaOptim to re-encode AAC files at a lower bitrate. Reducing from 256 kbps to 128 kbps saves approximately 50% with minimal audible difference.
Is AAC better than MP3?
Yes. AAC provides 20-30% better compression efficiency than MP3. A 128 kbps AAC file sounds as good as a 192 kbps MP3.
What bitrate should I use for AAC?
128 kbps for music (transparent for most listeners), 96 kbps for podcasts/voice, 64 kbps for spoken word. Apple Music uses 256 kbps AAC.
Can I compress iTunes purchases?
If you have DRM-free AAC files from iTunes (purchased after 2009), yes. MediaOptim can re-encode them at lower bitrates to save space.
Should I convert AAC to MP3?
No. Converting between lossy formats always degrades quality. Keep AAC format and adjust the bitrate instead. AAC is already more efficient than MP3.
Compress Your AAC Files Now
Save 40-60% on your AAC files. No quality loss. Everything stays on your Mac.
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