In Thailand you scan QR codes all the time: to pay at a noodle stall, read a café menu or join the guesthouse Wi-Fi. Here is what those black-and-white squares are, how your phone reads them so fast, and how to make one yourself on QR naka, free and without signing up.
What is a QR code?
QR stands for Quick Response: its designers cared above all about fast reading. It was developed in Japan in 1994 at Denso Wave, then a division of Denso that made barcode readers, because barcodes of the time held only about 20 characters.
A QR code is a 2D barcode. An ordinary barcode of bars is read along one line; a QR code arranges its dots both across and down, so it holds far more in a small square.
The developer kept the patent but declared it would not exercise it, and the QR code became an ISO standard in 2000 (today ISO/IEC 18004). Anyone can make or read one by the same rules.
The parts of a QR code
- Three big corner squares tell a reader where the code is and which way up. The inventors chose a pattern that almost never appears on printed forms. The QR naka generator warns that covering one of them stops the code reading.
- Small dots (modules): each dark or light cell carries a bit of your data.
- Recovery data (Reed-Solomon codes) lets a stained, torn or logo-covered code still read: level L recovers about 7%, M 15%, Q 25%, H 30%.
- The quiet zone, the blank margin, separates the code from the background; the generator notes that the standard asks for 4 modules.
Sizes are called versions, from version 1 (21×21 modules) to version 40 (177×177). More data needs more modules, so the dots get denser at the same print size.
How your phone reads it
- The camera finds the three corner squares, so the code reads from any angle, all 360 degrees.
- The software reads each cell as dark or light and turns the pattern back into data.
- Recovery data fills any unreadable cells.
- The phone offers the next step: open a website, join a Wi-Fi network, save a contact.
A plain QR code carries all its data in the pattern, with no server in between.
Why almost any phone can scan one
- It is an open standard, so a code made on one site reads in any ordinary QR reader.
- iPhone and iPad: Apple says to open the Camera app, hold the device so the QR code appears, then tap the link.
- Android: Android's guide says to open the camera app and point it at the code; there is also a QR scanner in Quick Settings, and Google Lens.
- Thai banking apps: PromptPay and bill payment QR codes follow the Thai QR Payment standard, so Thai banking apps can pay them. New to PromptPay? See PromptPay QR codes with an amount.
- On a computer: the QR reader reads a camera, a picture or a screenshot on your device, with nothing uploaded.
What a QR code can hold
| Data in the code | When scanned |
|---|---|
| Web link | Opens a web page, shop, form or shared file |
| Wi-Fi | Joins without typing the password |
| vCard | Saves name, phone, e-mail and address |
| Event | Adds date, time and place to the calendar |
| Text | Shows the message |
On QR naka these and more (LINE, map, call, SMS) are free as plain QR codes, with no sign-up and no ads.
Plain codes hold their data, so they never expire, but cannot be changed after printing. A tracked QR code holds a short link instead, so you can change the destination and count scans. Tracked codes are for members, starting with a 30-day free trial (membership page); the difference is explained in Do QR codes expire?
Make your first QR code
- Open the web link QR page, or the QR generator and pick "Web link" under "Kinds of QR".
- Paste your address into "Link". The code appears under "Preview and download".
- Check the "Size" shown, e.g. "3 · 29×29" (version 3, 29×29 modules); a short link keeps it low and scans more easily when printed small.
- To style it, open "Style" for colours, a logo or a frame. Keep dark dots on a light background: the page warns that light dots on dark fail on many phones.
- Test with a real phone, then press "Download PNG" for screens and chats, or choose SVG or PDF for the printer.
Where your data goes
Every untracked code is made in your browser: PromptPay numbers, Wi-Fi passwords and contact cards never reach QR naka. Signed in, the codes you download, copy, share or print are kept in your history. A tracked code's destination is stored at QR naka; scanners' IP addresses are not kept.
FAQ
Do I need the internet to scan a QR code?
Not to read a plain one; the data is in the pattern. A link needs the internet when you open the page.
Do QR codes expire?
A plain code has no expiry date and works as long as what it points to works. A tracked code works for as long as QR naka runs the service, or as its terms say.
Is it safe to scan a QR code?
Anyone can make one. Before opening a link, read the website name your phone shows, or the "Website" line in the QR reader. A payment QR shows only a number; the payee's real name appears in your banking app, so check it before you confirm. More in Fake QR codes: how to scan safely.
Ready? Make your first code on the QR generator, or see where a code goes in the QR reader.
