What is a QR code — how scanning a square works
What a QR code is: modules, error correction, Wi‑Fi and URL payloads, and how to generate one online.
A QR code is a matrix barcode. Dark modules encode the payload; a quiet zone around the square helps the camera lock on. Error correction (L, M, Q, H) lets a scuffed or logo-covered code still read.
Payloads are just text: a URL, WIFI:T:WPA;S:…, a vCard, geo:lat,lng. ToolsHelper draws the code in the browser, so the Wi‑Fi password never goes to a server.
A QR code is a square grid of modules. The three large corners are finders. Version number grows the grid as the payload grows. Error correction rebuilds a damaged patch and also makes the grid denser. The payload can be a URL, text, or a Wi-Fi string. This page defines the code. Building one for a link or a network is a converter.
FAQ
Which correction level with a logo?
Use H so the excavated center still decodes.
Can two colors be similar?
Low contrast fails scanners. Keep dark modules on a light field, or the inverse with enough contrast.