How do I convert AAC to FLAC?

Add your AAC file to the upload area above, then press Convert. The FLAC file downloads straight to your device. You do not need an account, and there is no watermark.

Are my files uploaded to a server?

No. This conversion runs entirely inside your browser using WebAssembly, so the file never leaves your device — you can even disconnect from the internet after the page loads and it will still work.

Does converting to FLAC reduce quality?

No. FLAC is a lossless format, so the conversion preserves exactly what is in your AAC file. Note that it cannot recover detail that was already discarded when the AAC was first created — a lossless container does not undo earlier compression.

How large a file can I convert?

Up to 300 MB per file for this conversion. Because the work happens in your browser, the practical limit is your device's memory — larger files work on a desktop with plenty of RAM and may fail on an older phone.

Can I convert several files at once?

Yes. Add as many as you like and press Convert All. Each file is processed independently, so one failure does not stop the rest, and you can download everything together as a ZIP.

Can I use this on my phone?

Yes. FileTools360 works in mobile browsers on iOS and Android, including choosing files straight from your camera roll. Very large videos may run out of memory on a phone — those are better converted on a laptop.

AudioLosslessRuns in your browser

AAC to FLAC Converter

Turn AAC files into FLAC in a couple of clicks. The successor to MP3 — better quality per bit. Lossless compression — CD quality at roughly half the size. The conversion is lossless — every pixel, sample or byte in the source is preserved.

On your deviceNever uploadedGone when you close the tabHow this works

Drop your files here

AAC files (.aac, .adts) · up to 300 MB each

or paste files from your clipboard

Ready when you are

Drop a AAC file above and FileTools360 will turn it into FLAC — right here on your device, without uploading anything.

⌘K to search converters

How to use it

1
Add your AAC files
Drag them onto the upload area, choose them from your device, or paste them from your clipboard. You can queue several at once.
2
Adjust the settings if you want to
The defaults suit most people. Open Advanced to control bitrate, sample rate and channels and start and end times.
3
Convert and download
Press Convert. Everything happens on your own device — nothing is uploaded. Download files one by one, or grab them all as a ZIP.

AAC and FLAC explained

AAC is the successor to MP3 and is the default audio codec for MP4 video, Apple Music and YouTube. At the same bitrate it generally sounds noticeably better than MP3.

FLAC compresses audio losslessly, typically to about half the size of WAV. Decompressed, it is bit-for-bit identical to the original — the compression is mathematical, not perceptual.

Where AAC files come from: Streaming services, video soundtracks and Apple devices.
Where FLAC is used: Hi-fi music libraries and archival rips of physical media.

AAC vs FLAC

The two formats solve different problems, which is why converting between them involves trade-offs rather than a straight upgrade.

AAC compared with FLAC
Property	Source	Target
Compression	Lossy	Lossless
Introduced	1997	2001
Browser support	Excellent across modern devices.	Great on desktop and Android; iOS support is newer.

AAC is stronger at: Better quality per bit than MP3. The standard audio track for MP4 video. Excellent device support.
FLAC is stronger at: Lossless — provably identical to the source. Roughly half the size of WAV. Rich metadata and cover art support.

Why convert AAC to FLAC?

People make this switch when they run into the limits of AAC: archiving, or targeting very old playback hardware. FLAC is the better fit when archiving music you may want to re-encode later, or storing CD rips.

AAC limitations that prompt the switch: Still lossy. Patent licensing applies to encoders. Slightly less universal than MP3 on very old hardware.
What you give up: Much larger than MP3 or AAC. Not supported natively by all portable devices.

Does converting AAC to FLAC reduce quality?

Going from AAC to FLAC moves already-compressed data into a format that stores it exactly. Nothing is lost from this point on, but nothing is recovered either — the detail AAC discarded when the file was first created is gone permanently. Expect a noticeably larger file for identical visual quality.