MP3 quality checker
Drop in an MP3, M4A, FLAC or WAV to see whether it is really the quality it claims. The checker reads the file’s frequency spectrum, finds where the audio stops, and compares that ceiling with the bitrate on the label. A “320 kbps” MP3 that stops at 16 kHz was made from a 128 kbps file, and a FLAC with an MP3 cutoff was never lossless. It runs entirely in your browser, so nothing is uploaded.
Your files never leave your computer: your browser reads and analyzes them locally. Nothing is uploaded.
| File | Real ceiling | Verdict |
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How it works
Every lossy encoder throws away the highest frequencies first, and the lower the bitrate, the lower it cuts. That cutoff shows up as a hard horizontal edge in the spectrum: detail below it, silence above it. Re-saving the file at a higher bitrate cannot bring those frequencies back, so the edge stays where the original encoder put it. The checker samples three 10-second windows from the track, finds the steepest drop, and maps its position to a bitrate:
- Above about 20.9 kHz, no hard edge: lossless-grade (a genuine FLAC, WAV or AIFF).
- About 19.5 to 20.9 kHz: a 320 kbps source.
- About 18.8 to 19.5 kHz: a 256 kbps source.
- About 18.0 to 18.8 kHz: a 192 kbps source.
- About 16.8 to 18.0 kHz: a 160 kbps source.
- About 15 to 16.8 kHz: a 128 kbps source.
- Below 15 kHz: 96 kbps or lower.
It uses the same method, and the same thresholds, as the audio quality scan in Crate Cleaner. The step-by-step manual method, with a free spectrum viewer, is in how to spot a fake 320 kbps MP3.
What the verdicts mean
- Looks genuine: the spectrum reaches the ceiling the bitrate should, or the file has no encoder cutoff at all.
- Can’t be sure: the high end fades out early, but gradually. That is typical of a dark master or a vinyl rip, not a transcode, so the checker will not call it fake.
- Probably upscaled: a hard cutoff one step below what the file claims. Worth a closer listen, and worth replacing if it is a track you play out.
- Fake (transcoded): a hard cutoff well below the claim, such as a 320 kbps label on a 128 kbps source, or a FLAC made from an MP3.
- Can’t judge: the file is silent, too short, or has a low sample rate that physically cannot hold the frequencies being tested.
When the checker can be wrong
It is built to protect real files, so it leans towards “can’t be sure” rather than “fake”. Still, keep these in mind:
- 320 vs 256 is a close call. Some encoders cut genuine 320 kbps files a little lower, close to where 256 kbps usually stops.
- AAC and Ogg cut differently from MP3. The ladder above is tuned for MP3, so treat M4A results as a guide.
- Browsers decode slightly differently. A borderline file can land one verdict apart in two browsers. Clear fakes and clear genuine files do not.
Found a fake? What to do
Replace it with a genuine copy from a store, your record pool or the original CD. Re-encoding it at a higher bitrate only makes the file bigger. If it is a track you rely on and you cannot replace it, keep it, but know it will sound dull on a big system. Duplicates are a common source of fakes: a better copy may already be in your library, which how to delete duplicate songs in Serato helps you find.
Check a whole library at once
This page checks a handful of files. Crate Cleaner’s Audio Quality scan runs the same test across your entire Serato library on your Mac, sorts every track into clean, warning, suspect and fake, and ranks what to replace first. The scan is free and unlimited, and it never changes your files.
FAQ
Is this MP3 quality checker free, and does it upload my files? It is free, with no sign-up, and nothing is uploaded. Your browser reads and decodes the file on your own computer; the audio never leaves it.
How can I tell if an MP3 is really 320 kbps? Look at its frequency spectrum. A genuine 320 kbps MP3 keeps content up to about 19.5 to 20 kHz. If the spectrum stops dead around 16 kHz, the file was made from a 128 kbps source and re-saved at 320.
Why does my 320 kbps file show as 256? Its cutoff sits between about 18.8 and 19.5 kHz, where 256 kbps encoders usually stop. Some encoders cut genuine 320 kbps files a little lower too, so a 256 reading on a 320 file is worth a closer listen rather than proof of a fake.
Can a FLAC file be fake? Yes. A FLAC made from an MP3 keeps the MP3's frequency cutoff, so it is lossless in format only. The checker flags a FLAC or WAV with a hard encoder cutoff as suspect or fake.
Can I fix a fake 320 MP3? No. Re-encoding cannot restore frequencies the original encoder threw away. The only real fix is a genuine copy from a store, a record pool or the original CD.
Which file types work? MP3, M4A and AAC, FLAC and WAV work in every modern browser. AIFF and Ogg depend on your browser. Very short or silent files cannot be judged.
Find every fake in your library
Crate Cleaner runs this check across your whole Serato library, free and unlimited, and ranks what to replace first.