AAC vs FLAC: Is AAC Lossless?
No — AAC is lossy and FLAC is lossless. Here's what that actually means for sound quality and file size, and when the bigger FLAC file is worth it.
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Convert FLAC to AAC →Is AAC lossless? No.
AAC is a lossy format. To shrink a file, it permanently throws away audio data — and that data can't be recovered. It's very good at choosing what to discard, so it sounds excellent for its size, but it is not a perfect copy of the original.
FLAC (Free Lossless Audio Codec) is lossless. It compresses audio with zero quality loss — decode a FLAC and you get back a bit-perfect copy of the source. The trade-off is size: FLAC files are much larger.
| Property | AAC | FLAC |
|---|---|---|
| Type | Lossy | Lossless |
| Quality vs original | Very good, not identical | Bit-perfect, identical |
| File size (3-min song) | ~5.8 MB (256 kbps) | ~20–30 MB |
| Best for | Everyday listening, mobile, streaming | Archiving, editing, audiophile playback |
| Apple ecosystem | Native | Not natively supported (use ALAC) |
| Open standard | Patented (licensed) | Free and open |
What the difference sounds like
For most people, in most conditions — phone speakers, earbuds, a car, a Bluetooth speaker — 256 kbps AAC and FLAC are indistinguishable. The gap only tends to matter on high-end gear in a quiet room, or when you're editing audio and every re-encode compounds loss. If you just want music that sounds great and takes little space, AAC is the practical winner. If you want a permanent, no-compromise master copy, FLAC is the one.
File size is the real trade-off
FLAC's honesty costs storage. A FLAC library is roughly 4–5× the size of the same music in AAC. On a phone or a small SSD that adds up fast. Many people keep a FLAC archive at home and sync AAC copies to their devices — best of both worlds.
Apple note
Apple devices don't play FLAC natively. Apple's equivalent lossless format is ALAC, which fits the same role as FLAC inside the Apple ecosystem. If you're comparing lossless options for an iPhone or Mac, read AAC vs ALAC.
Converting between them
- FLAC to AAC converter — shrink a lossless library into small, device-friendly AAC files
- AAC to FLAC converter — wrap AAC audio in FLAC (note: this can't restore the data AAC already discarded)
New to the format? Start with What is AAC? Comparing lossy options? See AAC vs MP3.
Free your storage — turn a lossless FLAC library into compact AAC files. No account, no software, no limits.
Convert FLAC to AAC →Frequently Asked Questions
Is AAC lossless?
No. AAC is a lossy codec — it discards audio data to save space. For lossless audio you need FLAC or ALAC.
Is FLAC better than AAC?
For pure fidelity, yes — FLAC is a perfect copy of the original. But it's 4–5× larger and isn't native on Apple devices. AAC is better for everyday listening and mobile.
Can I convert AAC to FLAC to make it lossless?
No. Converting AAC to FLAC wraps the already-lossy audio in a lossless container — it doesn't recover the data AAC threw away. FLAC only preserves quality when you start from a lossless source.
Which should I use for my phone?
AAC — smaller files, native support, and quality that's transparent for almost all listening. Keep FLAC for archiving if you want a master copy.