Convert FLAC to AAC — Free Online Converter
Convert Free Lossless Audio Codec (.flac) to Advanced Audio Coding (.aac) online for free. Fast, secure audio conversion with no watermarks or registr...
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Upload your .flac file by dragging it into the upload area or clicking to browse.
Choose your output settings. The default settings work great for most files.
Click Convert and download your .aac file when it's ready.
About FLAC to AAC Conversion
Converting FLAC to AAC transforms lossless audio into the most efficient lossy codec widely deployed today. AAC (Advanced Audio Coding) was developed as the successor to MP3 by the MPEG group and delivers better sound quality per bit than MP3 at every bitrate. At 256 kbps, AAC is considered transparent to the original source in double-blind tests by most listeners. This conversion is ideal when you need to shrink FLAC files for portable playback without the compatibility concerns of less common codecs.
Why Convert FLAC to AAC?
FLAC files average 800-1200 kbps, making them impractical for streaming or mobile storage. AAC at 256 kbps reduces file size by roughly 75% while retaining near-transparent audio quality. Apple devices natively play AAC but do not support FLAC without third-party software, so this conversion unlocks direct playback on every iPhone, iPad, Apple TV, and HomePod. AAC is also the mandatory audio codec for YouTube, Spotify (OGG internally but AAC for delivery), and most streaming platforms.
Common Use Cases
- Preparing a lossless music library for syncing to an iPhone or iPad via iTunes/Music app
- Creating high-quality audio files for podcast distribution where AAC is the recommended codec
- Reducing the size of FLAC archives for cloud storage while maintaining excellent audio fidelity
- Encoding audio for HTML5 web players that support AAC natively across all major browsers
- Producing AAC masters for delivery to Apple Music or iTunes Store submission
How It Works
FFmpeg decodes the FLAC bitstream and pipes PCM audio to the AAC encoder. The default encoder is aac (FFmpeg native), but libfdk_aac provides slightly better quality when available. AAC supports sample rates from 8 to 96 kHz, bit depths up to 32-bit float, and channel configurations up to 7.1 surround. The output is a raw AAC bitstream (.aac) or can be muxed into an M4A container for metadata and seeking support. Constant bitrate (CBR) and variable bitrate (VBR) modes are both supported.
Quality & Performance
At 256 kbps VBR, AAC is transparent for the vast majority of listeners and source material. At 128 kbps, quality remains very good for casual listening. Below 96 kbps, artifacts become noticeable on critical listening equipment. Since FLAC is lossless, the AAC output represents a single generation of lossy encoding — the best possible result short of another lossless format.
Device Compatibility
| Device | FLAC | AAC |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Native |
| iPhone/iPad | Partial | Native |
| Android | Native | Partial |
| Linux | Partial | Partial |
| Web Browser | No | No |
Recommended Settings by Platform
Spotify
Resolution: N/A
Bitrate: 320 kbps
OGG Vorbis preferred
Apple Music
Resolution: N/A
Bitrate: 256 kbps
AAC format required
SoundCloud
Resolution: N/A
Bitrate: 128 kbps
Lossless FLAC/WAV for best quality
Podcast
Resolution: N/A
Bitrate: 128 kbps
MP3 mono for spoken word
Tips for Best Results
- 1Use VBR mode for better quality-per-byte efficiency compared to constant bitrate
- 2Wrap output in an M4A container (.m4a extension) rather than raw .aac for proper metadata and seeking
- 3For Apple device playback, 256 kbps AAC-LC is the format Apple uses for iTunes Store purchases
- 4Preserve ReplayGain values from FLAC by converting them to iTunes Sound Check metadata in the M4A container
- 5If converting a large library, batch process alphabetically and verify a sample from each album before deleting the FLAC originals
Related Conversions
FLAC to AAC is one of the most common and practical audio conversions. Use 256 kbps VBR for high-quality archives or 128 kbps for space-efficient mobile playback. Wrap the output in an M4A container if you need metadata and chapter support.