Lossless Audio Checker — Spot Fake FLACs
Draw a full-size spectrogram of your file and look at the top of the picture. A lossy source leaves a sharp black shelf there — a real lossless file usually does not.
Free · No signup required · Your files stay private
What you can do with it
It opens at 4000×2000 with the frequency axis evenly spaced — the settings that make a cut-off at 16, 19 or 20 kHz jump out instead of hiding in a small picture.
An MP3 renamed to .flac takes the same shelf with it. One look tells you whether the file you just downloaded is worth the space.
Add up to 10 tracks at once and get an image for each, so a release that mixes real and upscaled files gives itself away.
How it works
Upload your file
We measure every frequency across the track and draw it as an image
Download the result
Frequently asked questions
How does the check work?
We draw a spectrogram: time across, frequency up, colour for loudness. MP3 and AAC encoders save space by throwing away the top of the spectrum, which leaves a sharp horizontal edge with nothing but black above it. That edge survives when the file is later converted to FLAC or WAV.
What does the cut-off look like?
A straight horizontal line across the whole picture with an empty band above it. Roughly 16 kHz points at a 128 kbps MP3, about 19 kHz at 192 kbps, and about 20 kHz at 320 kbps or AAC. A file that is genuinely lossless normally has content running right up to the top of the image.
Does a cut-off prove the file is fake?
No — treat it as strong evidence, not proof. Quiet acoustic recordings, old or badly digitised masters and some instruments genuinely carry very little energy up there, and a determined faker can add noise back above the shelf. A hard, dead-straight edge across a modern, busy track is about as clear as this test gets.
Why 4000×2000 and a linear frequency axis?
A small image blurs the top of the spectrum into a smudge, and a logarithmic axis squeezes the whole treble range into a thin strip. At full size with evenly spaced kilohertz, the top of the picture gets the room it needs and the shelf is unmistakable. Rendering that much detail takes a few seconds.
Which files can I check?
Any FLAC, WAV, ALAC, MP3, M4A or OGG up to 100 MB — plus video files, if you want to look at a soundtrack. Checking a file that is already MP3 works too; you will simply see the cut-off you expect.
Is it free, and do my files stay private?
Yes, it is free with no signup and no watermark. Your file is processed on our own servers and deleted automatically, and nobody else sees it. The download link is unguessable and is never listed or shared anywhere.
After the check
All free to try, no signup.
Automate it
Every tool here is also available to AI assistants and developers via our MCP server and REST API.
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Customer Reviews
Perfect even with opera, jazz, etc. It's like a dream...🥹
Perfect même avec de l'opéra , Jazz etc... Comme un rêve ...🥹
It's a bit annoying that I have to select the conversion type every time, and my initial selection doesn't stick. Other than that, everything's fine.
קצת מעצבן שכל פעם צריך לבחור סוג המרה ולא נשאר מה שבחרתי ראשון חוץ מזה הכל טוב
If you want to analyze everything from the individual instruments to the vocal arrangements in a song, VocalRemover is exactly what you need. You can listen to every component of your song in detail. I don’t usually leave comments, but I decided to leave one here because I imagine that if someone has made it this far and has doubts or needs encouragement to use VocalRemover, they should go ahead and do it—they won’t regret it!!
Si buscás estudiar desde cada uno de los instrumentos hasta cada arreglo vocal de una canción, vocalremover es lo que buscás. Podés escuchar cada componente de tu canción al detalle. No suelo dejar comentarios, pero decidí dejar uno acá porque imagino que si alguien llegó hasta acá y tiene dudas y necesita ánimo para usar vocalremover que lo haga tranquilo, no se va a arrepentir !!
Really great—the best of the best
muy buenazo mejor de lo mejor
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