Guides/QR Codes Explained: How They Work and How to Make One
QR Codes Explained: How They Work and How to Make One
QR codes went from a niche industrial tool to something you see on nearly every printed surface — menus, posters, business cards, product packaging, event tickets. Most people use them without thinking much about how they work: point your phone, something happens. But understanding what a QR code actually encodes, how it survives being crumpled or partially covered, and what the practical limits are, helps you use them more effectively — whether you are generating your own or evaluating whether a QR code is the right tool for what you are trying to do.
What a QR code actually stores
A QR code is a two-dimensional barcode that encodes a short piece of data — most commonly a URL, but also plain text, an email address, a WiFi network name and password, a phone number, a calendar event, or a contact card (vCard). The data is encoded into the pattern of black and white squares (called modules) that make up the code, along with information about how to decode it: the format, the error correction level, and a mask pattern that helps scanners read the code reliably.
The amount of data a QR code can hold depends on what kind of data it is: up to about 4,300 alphanumeric characters for plain text, or about 7,000 digits for numbers only. In practice, most QR codes hold a URL of a few dozen characters — far below the maximum. Trying to encode very long strings works technically but makes the code denser (more, smaller modules) and harder for cameras to read reliably, especially from a distance or at an angle.
How error correction lets damaged codes still scan
One of the most practical features of QR codes is built-in error correction: the data is stored with enough redundancy that a significant portion of the code can be damaged, obscured, or missing and the scanner can still reconstruct the full message. QR codes offer four levels of error correction — roughly 7, 15, 25 and 30 percent of the data can be lost and the code will still scan successfully.
This is why QR codes printed on materials that get scratched, crumpled, or partially covered — stickers, receipts, outdoor signage — usually still work. It is also what makes it possible to put a logo in the center of a QR code (a popular design choice): the logo covers some of the modules, but the error correction fills in the gap. Higher error correction produces a denser code because more redundant data has to fit, so there is a trade-off between robustness and physical size.
Static vs dynamic: what happens after you print
A "static" QR code encodes the data directly — the URL, the text, the WiFi password is baked into the pattern of squares. Once printed, it cannot be changed; the code will always point to the same destination. If that URL goes dead or you need to update it, you have to generate and print a new code.
A "dynamic" QR code takes a different approach: the code itself points to an intermediary URL (a redirect service), and you control where that redirect points. This lets you change the destination without changing the printed code — useful for marketing campaigns, menus that change seasonally, or any situation where you might need to update the link after the code is already on a physical surface. The trade-off is that you depend on the redirect service staying online; if it goes down, the code stops working, regardless of what it was pointing to.
When to use a QR code and when a short URL is better
QR codes are ideal for bridging a physical surface to a digital destination: a printed menu to an order page, a conference badge to a profile, a product label to a support page. The scanner replaces typing, which is the main value — nobody wants to type a URL from a poster. They also work well for sharing structured data that is hard to communicate otherwise, like WiFi credentials (scan to connect) or contact cards (scan to add).
For purely digital contexts — a website linking to another website, a message in a chat, an email — a QR code is almost never the right choice. If the user is already on a screen that can display a clickable link, making them point a camera at their own screen is adding friction rather than removing it. A plain hyperlink or a short URL does the same job with one tap instead of a camera interaction. The rule of thumb: QR codes connect physical to digital; links connect digital to digital.
Tools mentioned in this guide