Shim

QR codes

Nine QR tools sharing one encoder. Each one builds a different payload, because what a phone does after scanning depends entirely on how the text inside is shaped.

About qr codes

A QR code is a way of writing text as squares. Everything else is convention. Scan a code holding a plain web address and the phone offers to open it; scan one holding the same address prefixed with the right keyword and it offers to join a network instead. The squares do not know the difference, and neither does the encoder.

That is why these are separate tools rather than one page with a format dropdown. A WiFi code needs a network name, a password and a security type. A calendar event needs a title and two timestamps that have to be real dates. A vCard needs name fields that get split apart on the way in. Sharing a form between them would mean a page full of inputs that are mostly irrelevant to whatever you actually came to do.

What they do share is the encoder, and the rules about escaping. Several of these payload formats use punctuation structurally: a semicolon ends a field in the WiFi format, a comma separates values in a vCard, and a colon separates the number from the message in an SMS. Text containing those characters has to be escaped before encoding or the code carries something different from what you typed. That is the commonest defect in free QR generators and it is invisible until somebody scans the result.

Two practical notes. Longer content makes a denser pattern that needs printing larger to stay readable, so trimming tracking parameters off a URL before encoding is worth doing. And for anything printed, download the SVG rather than the PNG: a bitmap scaled up blurs the edges and scanners start failing at exactly the sizes you want.