Masahiro Hara led a two-person team at the Japanese company Denso Wave, unveiling the QR code in 1994. Traditional barcodes could only hold about 20 characters and had to be scanned from one fixed angle, which was slowing down factory and warehouse workers - Hara's team designed a code readable from any angle, more than ten times faster.

QR stands for Quick Response, a nod to the fast scanning speed Hara's team prioritized over raw capacity. Even so, the largest QR code (version 40, lowest error correction) can hold up to 7,089 numeric digits or 4,296 letters and numbers - though codes that dense become large and hard to scan reliably, so shorter content like a URL makes for a cleaner code.

Built-in Reed-Solomon error correction lets a QR code rebuild missing or damaged data from redundancy encoded elsewhere in the pattern. The "Error correction" setting above controls how much redundancy is added: level L (~7%) fits the most data into the smallest code, while level H (~30%) survives serious damage, useful when a logo sits in the middle of the code.

Not automatically - a QR code is just a container for a link or text, so it hides its destination until you scan it, a trick known as "quishing" when used for phishing. Treat an unexpected QR code, on a parking meter, a poster, or in an email, the same way you'd treat a suspicious link: check where it leads before entering any login details or payment information.