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MP3 vs AAC vs FLAC: which audio format?
By Himanshu Ranjan · Updated 8 November 2026
MP3 and AAC are lossy formats that discard some data to make small files; AAC generally sounds better than MP3 at the same bit rate. FLAC is lossless, decoding to an identical copy at about 50 to 70 percent of the original size. Use FLAC to archive, AAC for Apple devices, MP3 for maximum compatibility.
Lossy or lossless first
The key split is lossy versus lossless. MP3 and AAC are lossy: they reduce precision and discard data to shrink files. Wikipedia says MP3 can cut size by roughly 75 to 95 percent against CD audio, depending on bit rate. FLAC is lossless: it decompresses to an identical copy of the original audio, with files typically 50 to 70 percent of the original size.
MP3
MPEG-1 Layer III allows bit rates from 32 to 320 kbit/s, and 128 kbit/s is a common internet setting. It became a near-universal standard supported by portable players and phones. The last major US patent expired on 16 April 2017, and basic MP3 coding has been patent-free in the EU since 2012 at the latest. Choose MP3 when you need it to play anywhere.
AAC
AAC was designed as MP3's successor and generally gives better sound quality at the same bit rate. It supports more sample rates and channels, and its transform design gives higher compression efficiency. Apple announced iTunes and iPod support in April 2003, and iTunes Plus files were 256 kbit/s DRM-free AAC from May 2007. AAC is usually stored in an MP4 container with the .m4a extension. Choose AAC for Apple devices and streaming, where smaller files at good quality matter.
FLAC
FLAC is royalty-free and open, with a free reference implementation, and it was formally specified as RFC 9639 in December 2024. It supports metadata tags using Vorbis comments, cover art and fast seeking. Hardware support is less widespread than MP3, though it is built into Windows 10, Android, macOS and iOS (iOS support depends on the hardware). Choose FLAC to archive recordings and masters.
Remember the one-way rule: converting MP3 or AAC to FLAC does not restore what was discarded. The file gets bigger without getting better.
- Archive and editing: FLAC
- Music on Apple devices: AAC (.m4a)
- Podcast and universal sharing: MP3
- Voice recordings: AAC or MP3 at moderate bit rates
- Never re-encode lossy to lossy repeatedly
Converting on a Mac
FileDial has Convert › Convert to MP3, Convert › Convert to M4A and Convert › Convert to FLAC, each writing a new copy beside the original. Audio › Extract audio as MP3, Audio › Extract audio as M4A and Audio › Extract audio as AAC pull sound out of video files. Tags › Remove tags makes a copy without tags before sharing. Always convert from your best source: record or rip to FLAC or WAV, then make lossy copies from that.
For size-focused jobs, see the audio compression guide, and for WAV sources see the WAV to MP3 guide.
- Keep your best source file untouched.
- Select the file in Finder and open the dial.
- Choose Convert › Convert to M4A for Apple devices or Convert › Convert to MP3 for compatibility.
- Compare file sizes on the result card and listen to a section.
Mistakes and practical advice
The first mistake is re-encoding lossy to lossy. Converting an MP3 to AAC, or an AAC to a lower-bit-rate MP3, stacks losses and can add audible artifacts. Always make lossy copies from the best source you have, ideally a WAV or FLAC master.
The second is believing a higher bit rate fixes a low-quality source. Converting a 128 kbit/s MP3 to 320 kbit/s makes the file larger without restoring anything. Likewise converting MP3 to FLAC gives a lossless copy of already damaged audio.
The third is choosing by file extension. An .m4a file can hold AAC or Apple Lossless, and the MP4 container family also holds other codecs. Judge by codec and bit rate rather than extension alone.
Fourth, forgetting tags and cover art. Converting can drop tags, and FLAC uses Vorbis comments while other formats use their own schemes. Check artist, title and artwork after conversion. If you want a copy without personal tags for sharing, Tags › Remove tags writes one.
Fifth, ignoring the listening context. In a car or with earbuds in a noisy place, the difference between a good AAC and FLAC is hard to hear, and storage is better spent elsewhere. On good headphones or studio monitors, lossless matters more, especially for editing masters.
Finally, speech is different from music. A podcast or voice memo rarely needs high bit rates, and tools like Clean › Clean up voice and Clean › Remove background hum in FileDial improve the source before you encode. See the compress audio and trim audio guides for size and length.
Questions
Is FLAC better than MP3?
FLAC is lossless, so it keeps all the original audio, while MP3 discards some to save space. FLAC files are larger, typically 50 to 70 percent of uncompressed size. Whether you can hear a difference depends on your equipment, the music and the MP3's bit rate.
Is AAC better than MP3?
At the same bit rate AAC generally sounds better, according to Wikipedia, because its design is more efficient. MP3 remains the safest choice for universal compatibility, especially with older players, cars and hardware that predate AAC or lack support for it.
Will converting MP3 to FLAC improve quality?
No. The information MP3 discarded cannot be recovered, so converting to FLAC produces a larger file with the same sound, now stored losslessly. Only convert to FLAC if you want a stable archive copy of what you already have, not to improve it.
What format should I use for a podcast?
MP3 is the usual choice for compatibility, at a moderate bit rate for speech. AAC also works in many apps. Check your hosting platform's current requirements, and keep a lossless master of the raw recording so you can re-export later if requirements change.