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QR code anatomy explorer

Published 7 September 2026

  • Version 3, 29×29 modules, error correction M, mask 0. Tap a label to isolate it.

Runs entirely on your device. Nothing you enter or upload is sent to a server.

Reading the colors

  • Finder patterns (purple): the three big squares. They tell the scanner where the code is and which way up.
  • Separators: a one-module white border around each finder.
  • Timing patterns (orange): alternating dark and light between the finders, so the scanner can count modules.
  • Alignment patterns (green): small squares that let the scanner correct for a curved or tilted surface. Version 1 has none; larger versions have many.
  • Format information (red): 15 bits, stored twice, giving the error-correction level and the mask. The masking and Reed–Solomon article shows the eight masks and how the encoder picks one.
  • Version information (teal): from version 7 upwards, 18 bits saying which version this is.
  • Data (black and white): your content plus error-correction codewords.

Try it yourself

Now that you can see the parts, the explainer walks through what the scanner does with each of them.

How a QR code works

Frequently asked questions

▸What is the mask pattern?

One of eight XOR patterns applied to the data area so that no large blank or dark regions form, and so it never resembles a finder pattern. The encoder tries all eight and picks the one with the lowest penalty score.

▸Why is there a lone dark module near the bottom-left finder?

It is always dark, by specification. Decoders use it as a reference. It sits beside the format information.

▸Where is my actual text?

In the white and black modules labeled data, read in a zigzag from the bottom-right corner upwards, two columns at a time.

Related reading

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