How QR Codes Work (and How to Make One Free)
Invented in 1994 for Toyota's factories, now scanned billions of times a day. What's actually inside those little squares?
From factory floors to restaurant menus
QR stands for Quick Response. A Toyota engineer designed the code so car parts could be scanned fast — 10× faster than the barcodes of the era. The big square pattern holds far more data than a one-dimensional barcode: up to about 4,000 alphanumeric characters, enough for a long URL, contact details or a short message.
How the pattern stores your link
A QR code looks random but is carefully structured:
- The three large squares in the corners are finder patterns — they let the scanner locate and orient the code at any angle, even upside down
- The smaller fourth square is a timing pattern that helps calibrate size
- Stripes of error-correction data mean the code still scans even when up to 30% of it is dirty, torn or covered by a logo
- The remaining dots encode the actual content — your URL — in binary
Why they "never" wear out
A QR code for a link isn't connected to a service that can expire — it's just text, encoded. The same code works for decades. What can change is the destination: if the URL it points to dies, the code stops leading anywhere. For permanent print materials, point QR codes at URLs you control (your own domain or a short-link service you manage).
Make your own in seconds
The ToolCaptain QR Code Generator turns any link or text into a downloadable PNG — pick a size from 128 to 1024 pixels, generate, done. It all happens in your browser, so nothing about your (possibly not-yet-public) link is sent to any server.
- For print (menus, flyers, posters): choose 512 or 1024 px
- For screens (slides, websites): 256 px is plenty
- Long URL? Shorten it first — shorter links produce simpler codes that scan faster and print cleaner
Frequently asked questions
Can QR codes be dangerous? The code itself is just text — the risk is the destination. Preview the URL before opening, as your phone's camera usually lets you do.
Do QR codes expire? No — but keep the destination URL alive and use HTTPS.
How small can a QR code be? In print, around 2×2 cm is the practical minimum for reliable scanning.