Upload a AAC file and get a FLAC back. No signup, no watermark, no limit on how many.
AAC is MP3's designated successor and wins at low bitrates by a clear margin. A bare .aac file is the raw ADTS stream rather than the .m4a container most software expects.
Where you run into it: YouTube and streaming audio tracks, broadcast, anything that came out of a device rather than a music shop.
What it costs you: The naked .aac extension confuses a surprising amount of software, which is the usual reason people convert it.
FLAC compresses losslessly: it typically halves a WAV and gives back bit-for-bit the same audio when decoded. It is free, open, and widely supported outside Apple's world.
Where you run into it: Archived rips, Bandcamp and Qobuz downloads, anyone who keeps a music library they intend to still have in ten years.
What it costs you: Half of enormous is still large, and some hardware — car head units especially — will not touch it.
A bare .aac is a run of AAC frames with no file header at all, and FLAC is very nearly its opposite: a format with a header block stating the length, the rate and the depth, a seek table so players can jump instantly, and a checksum of the audio it contains. Decoding the stream and compressing it again losslessly is therefore a substantial structural upgrade to something that was barely a file. The audio itself arrives unchanged from the capture, damage and all.
Think about whether you want this at all. Nearly every bare .aac is a capture — a radio stream, an HLS segment, a broadcast tool's export, a dashcam — and a lossless archive of a lossy capture costs eight times the space for audio that is no better. If the aim is preservation, the original .aac is both the more faithful archive and the cheaper one. FLAC earns its place when the file has to be usable rather than merely kept: it seeks, it reports its length, it holds tags, and software that flatly refuses raw AAC will take it without complaint.
Yes, entirely, and there is no cap on how many files you convert. No account, no watermark, no trial.
Nothing more is lost and nothing recovered. One artefact does come along for the ride: a raw stream carries no metadata telling the decoder how much of the encoder's own priming to discard, so the audio starts roughly a thousand samples — about 23 milliseconds — after the beginning of the file. FLAC records that faithfully, like everything else. Trim it in an editor if the result has to line up with anything.
Five to eight times the .aac, which is a great deal to pay for a capture. The figure is also hard to predict in advance, because a raw stream does not declare its duration — nothing can tell you how long the file is until it has been decoded, which is one of the reasons these files behave so badly in players in the first place.
Yes — FLAC is one of the formats this converter writes, so the reverse page exists at /flac-to-aac/. The trip out is exact, because FLAC discards nothing — it is the return to AAC that re-encodes. A round trip therefore costs one more generation rather than two, and the FLAC in the middle was never an improvement on the AAC you started with.
The file is uploaded to do the conversion — nothing here runs in your browser — and both your upload and the converted result are deleted the moment the file is sent back. Nothing is stored and nothing is logged beyond the request itself.