Is your FLAC really lossless?
A FLAC converted from an MP3 is as big as the real thing, but the lost audio never comes back. Drop your files: the tool measures the frequency cutoff and tells you whether they came from a lossy source.
or drop FLAC, WAV or AIFF files here. Your files never leave your computer.
| File | Format | Cutoff | Result |
|---|
How does it tell?
MP3 and AAC encoders cut everything above a certain frequency to save space. After converting to FLAC, that cut stays in the spectrum as a steep wall:
- 128 kbps: about 16 kHz
- 192 kbps: about 18–19 kHz
- 320 kbps: about 20 kHz
- Truly lossless (44.1 kHz): audio up to 21–22 kHz
What it can't tell
This isn't proof. Older recordings and some masters naturally fade in the highs; the tool treats a gentle roll-off as such and doesn't call it lossy. It may miss files that came from a lossy source and were processed afterwards. If in doubt, look at the spectrogram yourself.
Frequently asked questions
What is a fake FLAC?
A lossy file (usually an MP3) converted to FLAC. It's as large as a real FLAC, but the audio the MP3 threw away doesn't come back, so it sounds the same as the MP3.
What should I look for in the spectrogram?
The high frequencies. In a truly lossless track, the colours reach all the way to the top unevenly; in a file converted from MP3 they stop at a flat line and the area above is empty.
Are my files uploaded anywhere?
No. The check runs in your browser, on your computer; your files are never sent to a server.