ExplainerTools

Short · Codes

Why does a torn QR code still scan?

Many of a QR code's squares are backup: Reed–Solomon math built from your link. Tear a chunk out and it still scans; damage a corner finder and it fails.

Try it yourself

Opens QR Repair Lab. Change the same thing yourself.

Narrated · 33 seconds · captions includedDownload the film

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Transcript

Why does a torn QR code still scan? Because it was built expecting damage. Many of those little squares aren't your link at all. They're backup: extra math, built from your link, that can rebuild missing pieces. Now tear a chunk out. Still scans. At the strongest setting, almost a third of the code can be lost. Just don't touch the three big squares in the corners. They tell the camera where the code is. Try it yourself at Explainer Tools dot com.