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FLAC Checker & Hi-Res Audio Fraud Detector

Is your "192 kHz hi-res" file actually an upsampled 44.1 kHz recording? Drop any file and this tool answers by looking at where the energy actually stops (the spectrum), not what the file extension claims. A genuine hi-res master has continuous energy above 22 kHz; a fake cuts off sharply at the original master's Nyquist limit (half its sample rate - the highest frequency it can hold), with nothing above the brick wall.

Try it: drop in any track you own - a FLAC, WAV, ALAC, MP3 or AAC - or click a demo below to see what a real hi-res file vs an upsampled fake looks like.

My analyses

Every checked file lands here automatically. Stays on this device only.

Verdict
Awaiting file Drop an audio file below to check it.
Highest real content - Where the spectrum drops below the noise floor.
File format - Sample rate x channels x duration.
No file handy? Try a demo:

All analysis is local. Files never leave your device.

How to read the spectrum

What to look for

A genuine hi-res recording (96 kHz or 192 kHz) shows continuous energy extending above 22 kHz, though the level drops with frequency due to natural program-content rolloff. The key is no abrupt brick-wall cutoff below 22 kHz.

A fraudulently upsampled file shows a sharp, near-vertical dropoff at 20-22 kHz, the fingerprint of the original 44.1 / 48 kHz recording's anti-aliasing filter. Especially common with "hi-res" releases on some stores.

What it cannot prove

Even if a file has genuine hi-res content above 22 kHz, that doesn't automatically mean it sounds better than a well-mastered 16/44.1 file. The source master quality matters more than the format.

This tool analyses format authenticity only. A 96 kHz file genuinely recorded and mastered at 96 kHz is authentic. One mastered at 44.1 and exported at 96 kHz is a storage waste.

Audio formats and what their spectrograms should look like

Sample rate is the upper bound; Nyquist (rate ÷ 2) is the highest frequency a format can encode. Genuine 192 kHz files have energy above 22 kHz; fakes cut off sharply at the original master's Nyquist limit.

FormatSample rateNyquistSpectrogram tells
MP3 320 kbps44.1 kHz22.05 kHzHard cutoff around 16-19 kHz from the codec lowpass.
AAC 256 kbps44.1 kHz22.05 kHzCutoff near 19-20 kHz; cleaner than MP3.
CD (Red Book)44.1 kHz22.05 kHzBrick wall at 22 kHz. Nothing above.
DVD-Audio / pro standard48 kHz24 kHzBrick wall just below 24 kHz.
"Hi-Res" 24/88.288.2 kHz44.1 kHzGenuine: tapered roll-off into 30+ kHz.
"Hi-Res" 24/9696 kHz48 kHzGenuine: continuous energy past 22 kHz.
"Hi-Res" 24/192192 kHz96 kHzGenuine: reaches 40 kHz+. Fakes show the 22 kHz wall.
DSD64 (SACD)2.8 MHz (1-bit)~28 kHz audioRising noise floor above 25 kHz - DSD signature.
DSD128 / 2565.6 / 11.3 MHz~50 / ~100 kHzCleaner band. Same rising noise above the audible limit.

How to tell real hi-res from an upsampled file

A digital recording cannot contain any frequency above half its sample rate - the Nyquist limit. A genuine 96 kHz file can therefore hold content up to 48 kHz, and a 44.1 kHz file stops hard at 22.05 kHz. That ceiling is a property of the format, not of the music.

Converting a 44.1 kHz file to 96 kHz changes the container without adding anything. The Nyquist limit moves up, but the content does not: the spectrum still stops dead at 22.05 kHz, leaving a sharp horizontal edge with empty space above it. That edge is the signature of upsampling.

A real high-rate recording looks different. Energy tapers off gradually into the ultrasonic rather than stopping at a wall, because microphones and instruments have no reason to end at exactly the old limit. Reading a spectrogram for that difference is a reliable way to spot a file sold as hi-res that is not.

The hi-res audio checker after analysing its built-in demo file: a verdict on whether the file is genuinely high resolution, the highest real frequency content found, and the container format.

Worked example

The tool's own bundled demo file, a genuine 96 kHz mono recording, dropped straight in.

Verdict genuine hi-res, highest real content 48.0 kHz, container 96 kHz.

The verdict follows the highest real content and never the container. A fake declares the same 96 kHz in its header and stops dead at 22 kHz, which is exactly what the second demo file on this page shows.

The ideas behind the controls

Nyquist frequency
Half the sample rate, and the hard ceiling on what a file can contain. 22.05 kHz for CD, 48 kHz for 96 kHz audio.
Brick wall
A sharp horizontal cut-off in the spectrogram with nothing above it. Characteristic of upsampled material.
Lossy artefacts
The cut-off a codec leaves, often around 16 to 20 kHz, plus gaps where quiet bands were discarded. Visible even after conversion to a lossless container.
Spectrogram
Frequency against time, with brightness for level. It shows the shape of the top octave, which is where all of these clues live.

FLAC and hi-res audio fraud FAQ.

What fake hi-res actually is, how the FFT detector spots it, whether a FLAC can be a transcoded MP3, and whether anyone can hear the difference.

  1. What is a fake hi-res audio file?

    A file that claims a high sample rate (96 kHz, 192 kHz) or bit depth (24-bit) but actually contains content from a lower-resolution source, typically upsampled from a 44.1 kHz CD master or, worse, a lossy MP3. The container says hi-res; the audio is not. This is widespread in some streaming catalogues.

  2. How does the FLAC & hi-res checker work?

    It runs an FFT (fast Fourier transform) on your file and plots the actual frequency content. A genuine 96 kHz file shows energy up to 48 kHz; a 192 kHz file up to 96 kHz. A fake hi-res file shows a hard brick-wall cutoff around 20-22 kHz, the giveaway that the audio came from a 44.1 kHz source, regardless of what the container claims.

  3. Can I hear the difference between real and fake hi-res?

    Almost never directly. Human hearing tops out at 20 kHz and falls fast above 16 kHz with age. The case for hi-res is mostly about the master, not the format: real hi-res releases often come from better masters with more dynamic range. The detector tells you whether you are getting the high-rate content you paid for.

  4. Is my FLAC actually lossless, or transcoded from an MP3?

    The same spectrum test answers that one. A lossy encoder discards the top of the band and lowpasses what is left, so an MP3 at 320 kbps stops dead around 16 to 19 kHz and AAC around 19 to 20 kHz. Re-encode that into FLAC and everything from then on is lossless, but the missing top never comes back and the brick wall sits exactly where the encoder left it. A FLAC ripped from a CD runs on to the 22 kHz Red Book wall instead. Drop the file in and read where the energy stops.

  5. Which file formats can this checker read?

    Anything your browser can decode: FLAC, WAV, AIFF, ALAC, MP3, AAC and OGG. The analysis runs on the decoded audio rather than the container, which is the whole point - the file extension, the sample rate in the header and the metadata are precisely the things a fake gets right.

  6. Does the file get uploaded to your server?

    No. The FFT analysis happens entirely in your browser using the Web Audio API. The file is decoded into an AudioBuffer locally, analyzed, and discarded when you close the page. We never see your audio files.