What is a QR code?
A QR code (Quick Response code) is a two-dimensional barcode that stores text in a square grid of black and white modules. Unlike a classic barcode it is read in both directions, which is why it holds a few thousand characters instead of a dozen digits, and why any phone camera can decode it from any angle.
What the phone does with the decoded text depends on how that text is formatted. A plain web address opens a browser, a line starting with WIFI: offers to join a network, a vCard block offers a new contact entry. That is the only difference between the pages here:
- URL: opens a website.
- WiFi: joins a wireless network without typing the password.
- vCard: saves a contact into the address book.
- E-mail: opens a new mail with recipient, subject and text prepared.
- SMS: opens the messaging app with number and text prepared.
- Text: shows plain characters and does nothing else.
Error correction and size
QR codes carry redundant data so they still scan when part of the symbol is dirty, creased or covered. Level L recovers about 7% of the code, M about 15%, Q about 25% and H about 30%. More correction means more modules for the same content, so the code gets denser. M is the sensible default; choose H only when the code will be printed small, on packaging, or with a logo placed over it.
Download the result as PNG for screens and quick printing, or as SVG when it has to scale: a vector file stays sharp on a poster, a shop window or a vehicle wrap. Every code generated here is static, which means it encodes the content directly and keeps working forever - there is no redirect service in between that could expire.