AAC to FLAC Converter

Convert AAC to FLAC Online

Wrap your AAC audio in FLAC, the open, royalty-free lossless container maintained by the Xiph.Org Foundation. One honest caveat up front: AAC is a lossy format, so FLAC cannot recover detail AAC already discarded — think of it as making a perfect digital copy of a photocopy. What it does give you is a stable, patent-free master that survives future re-encodes and plays on lossless-only DACs, streamers, and music servers.

How to Convert AAC to FLAC

1. Upload Your AAC File: Drag and drop your .aac file onto the page, or click "Add Files" to browse. You can queue several files and convert them with the same settings.
2. Set the Compression level: Open Advanced Options and use the Compression level slider (1 to 12). FLAC is lossless at every setting, so this only changes file size and encode time — never the audio. Higher is smaller, lower is faster.
3. Adjust Audio Channel or Sample Rate (optional): Leave both on Original to keep an exact lossless copy of the source. Choose Mono or a lower Sample Rate only if you deliberately want a smaller file.
4. Convert and Download: Click Convert and save your .flac file. No sign-up, no watermark.

AAC vs FLAC at a Glance

Frequently Asked Questions

Does converting AAC to FLAC improve the sound quality?

No. AAC is lossy, so the detail it threw away during its original encode is gone for good, and FLAC cannot reconstruct it. The FLAC file is lossless relative to the AAC — bit-for-bit identical to what you fed in — but it is not closer to the original studio master. If you want genuine lossless audio, you need a FLAC ripped from the CD or a lossless download, not one made from an AAC.

If there's no quality gain, why convert AAC to FLAC at all?

Two practical reasons. First, it stops a "lossy-to-lossy" cascade: if you later need MP3 or Opus for a phone, re-encoding from FLAC avoids the extra generation loss you'd get re-encoding straight from AAC. Second, plenty of audiophile DACs, network streamers, and library managers prefer or require a lossless container, and FLAC's metadata and album-art tagging is more robust than AAC's.

Will the FLAC file be larger than my AAC file?

Yes, usually several times larger. FLAC losslessly stores the full decoded waveform, so a 128 kbps AAC track (roughly 1 MB per minute) typically balloons to FLAC sizes measured in the high single-digit MB per minute. You are trading disk space for a stable, patent-free master — if your goal is a smaller file, FLAC is the wrong target; use the Audio Compressor instead.

What does the Compression level slider actually do?

It controls how hard the encoder searches for efficient ways to pack the audio. Per the Xiph.Org FLAC FAQ, every level decodes to bit-identical audio — higher settings only shrink the file and take longer to encode, while decode speed is unaffected. In our testing, moving the slider from a low to a high setting on a 3-minute track changed the output size by a few percent with zero change to the decoded waveform.

Does FLAC preserve the bit depth and sample rate of my source?

FLAC supports linear PCM from 4 to 32 bits per sample and sample rates from 1 Hz up to 655,350 Hz, so it comfortably holds whatever your AAC decodes to. Leave Audio Channel and Audio Sample Rate on Original to keep an exact copy; only change them if you specifically want to downmix to Mono or resample.

Can I convert the FLAC back to AAC later without extra loss?

Going FLAC back to AAC is still a lossy step, so that re-encode adds its own generation loss — but because FLAC is a clean, lossless source, the result is no worse than starting from your original AAC, and often the workflow is simpler. Use FLAC to AAC when you need the smaller Apple-friendly file again.

How are my files handled during conversion?

Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark, never shared or made public. The main practical limit on a big batch is upload size and time, not your device.