FLAC to AAC Converter

FLAC vs AAC — What You Gain and What You Give Up

FLAC keeps every bit of the original recording, which is exactly why one album can run into the hundreds of megabytes. AAC throws away the parts a perceptual model judges inaudible and gets you a library that fits on a phone. The decision is genuinely one-way: FLAC to AAC is a lossy step, and no later conversion recovers what it discards. So the short answer is to keep the FLAC files as your masters and treat the AAC as a listening copy — then the only remaining question is what bitrate to spend, which the rest of this page works through.

Side-by-side Comparison

When to Stay on FLAC

• The files are your only copy. Once you have converted and deleted the originals, there is no route back.
• You expect to edit, re-master or re-encode later — every lossy generation compounds on the last.
• The playback chain is a computer, a NAS or a modern browser, all of which handle FLAC natively and where storage is cheap.
• You care about bit-exactness for its own sake: verification, checksums, archival deposit.

When to Convert to AAC

• Storage is the binding constraint — a phone, a watch, a car head unit, a plane's worth of offline listening.
• The destination is Apple hardware or software, where AAC is the native lossy format.
• You are sharing casually and the recipient does not want a 400 MB download.
• The source material does not reward lossless anyway: spoken word, podcasts, audiobooks, field recordings.

How to Convert FLAC to AAC

1. Upload Your FLAC Files: Drag and drop your .flac files onto the page, or click "+ Add Files" to browse. Multiple tracks queue and convert with the same settings.
2. Pick a Bitrate Mode Under File Compression: The page starts on Quality Preset, the automatic, hands-off mode and the least predictable control here; nothing is pre-selected in it either, so leaving it alone hands the decision to the server's own default rather than the rung on screen. Do not stop there. For music, switch to Constant Bitrate and choose an explicit rate — 256 kbps is the usual near-transparent target, and the dropdown runs from 8 up to 384 kbps.
3. Adjust Channels, Sample Rate or Trim (Optional): Audio Channel and Audio Sample Rate each offer an Original setting, which is what you want for music; Trim exports only a section if that is all you need.
4. Convert and Download: Click "Convert" and save your .aac files individually or as a ZIP. No sign-up, no watermark.

Bitrate Modes on This Page

Note the asymmetry: Variable Bitrate here tops out at the 96k–112k range, so it is a size-first mode rather than a quality-first one. If you want a genuinely near-transparent music encode, Constant Bitrate at 256 kbps is the setting to use.

Frequently Asked Questions

Will I lose audio quality converting FLAC to AAC?

Yes — that is the trade, and it is worth naming honestly. FLAC decodes to the exact original PCM samples, while AAC applies a perceptual model that removes detail it predicts you cannot hear. At 256 kbps that prediction is good enough that most listeners cannot reliably distinguish the result from the source in a controlled comparison, but the discarded information is gone for good. Our pipeline decodes and re-encodes rather than repackaging, so there is no lossless path through this page. Keep the FLAC files.

What bitrate should I choose, and why does Variable Bitrate stop at 96–112 kbps?

For music, use Constant Bitrate at 256 kbps; 320 kbps if you want headroom and do not care about the extra size. The Variable Bitrate dropdown deliberately offers only lower ranges — 20k–32k through 96k–112k — because those quality-targeted modes are aimed at speech and small-file use cases. It is not a ceiling on what AAC can do, just on what that particular mode exposes. If a VBR range looks tempting for music, take the equivalent constant rate instead; you will get a better result and a predictable file size.

Should the output be .aac or .m4a?

This page writes a bare .aac stream — AAC audio in an ADTS wrapper with no container around it. That is fine for many players and is the right answer when a system specifically wants raw AAC. For a music library it usually is not: .m4a puts the same AAC audio inside an MP4 container, which carries tags, artwork and chapter information and is what Apple software expects. Same codec, better packaging — use FLAC to M4A if the files are going into a library rather than into a pipeline.

Will a bare .aac file play in a browser?

Do not count on it. MDN describes AAC support as "somewhat less predictable" because the codec is patent-encumbered: Firefox only supports it when the operating system or an external library provides it, and Chrome supports AAC only in MP4 containers, and only AAC's Main Profile — a raw ADTS .aac file falls outside that. AAC is also absent from Chromium builds entirely. If the audio needs to play from a web page, either wrap it in MP4 via FLAC to M4A or use a format with broader documented support.

Is AAC really better than MP3 at the same bitrate?

At the bitrates people actually use, generally yes — AAC was designed as MP3's successor and its coding tools let it hold more detail per bit, which shows most clearly below about 128 kbps. The gap narrows as bitrate rises; at 256 kbps and above both are close enough to transparent that codec choice matters less than the encoder settings. The real reason to prefer one over the other is usually compatibility, not fidelity: MP3 plays on essentially anything ever made, which is why FLAC to MP3 remains the safer pick for an old car stereo or a stubborn device.

How much smaller will my files actually get?

Work it from the bitrate. CD-quality stereo PCM runs at 44,100 × 16 × 2 = 1,411 kbps, about 10.6 MB per minute. FLAC typically brings that down to roughly half or two-thirds depending on how busy the music is, so call it 5–7 MB per minute. AAC at 256 kbps is 256 × 60 ÷ 8 = 1,920 kB, about 1.9 MB per minute — so around three times smaller than the FLAC. At 128 kbps it is 0.96 MB per minute, closer to six times smaller. Multiply by track length for a realistic estimate before you commit.

Can I get back to FLAC from the AAC later?

Only in the trivial sense that you can wrap the AAC's decoded output in a FLAC file — and that is a bad idea. FLAC would losslessly preserve the already-damaged audio, giving you a large file with none of the original's detail restored. The information AAC removed is not recoverable by any tool. This is the whole reason to keep your FLAC originals: they are the master, and every lossy copy is derived from them rather than replacing them. If you need a smaller lossless file, compress the FLAC itself rather than converting it.

How are my files handled, and how long are they kept?

Your FLAC files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours. There is no sign-up, no watermark, and your files are never shared or made public. FLAC uploads are large by nature, so upload time is the slow part of any big batch — if you are only reshaping existing lossy audio rather than converting a lossless master, the Audio Compressor works on the format you already have and moves far less data.