QR codes (Quick Response codes) are two-dimensional barcodes invented by Denso Wave in 1994 for automotive manufacturing tracking. They encode data in a matrix of black and white squares that smartphone cameras can decode instantly. QR codes use Reed-Solomon error correction — the same mathematics used in CDs and DVDs — to remain scannable even when partially damaged or obscured. This is why you can place a logo in the center: the error correction algorithm reconstructs the hidden data modules. The four error correction levels (L/M/Q/H) control how much redundancy is added, with High (H) allowing up to 30% of the code area to be obscured while maintaining scannability.
Static QR codes — like those generated by this tool — encode data directly into the code pattern. They work permanently with no server dependency, subscription cost, or expiration date. Dynamic QR codes (offered by paid services) use a redirect URL that can be changed after printing, but require an active server. For permanent destinations like your website homepage, contact card, or WiFi credentials, static codes are the better choice — they are faster to scan, more reliable, and completely free. Always test generated QR codes on multiple devices (iPhone and Android) and in the actual lighting/distance conditions where they will be scanned.