How to create a QR code (link, Wi-Fi, contact) that scans reliably

What a QR code is and how it works

A QR code is a two-dimensional barcode: a grid of modules (the black and white squares) that a camera reads in an instant. It was invented by Denso Wave to label car parts, and has been an international standard since 2000. Denso Wave waived the rights to its patent for standardized QR codes, so anyone can create and use them freely.

A QR code's size depends on how much data it holds: version 1 is 21 × 21 modules and the largest, version 40, is 177 × 177, with 4 more modules per side at each version. More data means more modules and a denser code, which has to be printed larger to scan well.

How much data fits

The maximum capacity, at the lowest error correction level (L) and version 40, is 7,089 numeric characters, 4,296 alphanumeric characters or 2,953 bytes in binary mode. In practice you will not get near those limits, and you would not want to: the less content, the simpler the code and the better it scans. For a long link, use a short one or a page of your own to redirect from.

How to create a QR code, step by step

1. Open the QR code generator.
2. Choose what the code should contain (see the types below) and fill in the details.
3. Adjust the colour (dark on a light background) and the error correction level.
4. Download the result as PNG (for documents, websites and screens) or SVG (for print shops, posters and signs: it scales without losing sharpness).
5. Test it with your phone before printing or publishing it.

The generator runs in your browser, so the content of the code is not sent anywhere, and the codes you create do not expire, carry no watermark and depend on no account.

The most useful content types

A QR code for a link

It opens a web page when scanned. It is the most common use: restaurant menus, posters, business cards, flyers. Check that the link works and that you type it in full.

A QR code for Wi-Fi

Whoever scans it joins your network without typing the password. The code contains the network name (SSID), the security type and the password in a standard syntax like WIFI:T:WPA;S:mynetwork;P:mypassword;;, which Android and iOS 11 or later recognise. In it, T is the encryption type (WPA, WEP or nopass if there is no password), S is the SSID and P the password; if the network is hidden, H:true is added. Special characters (\, ;, ,, " and :) are written with a backslash in front, which the generator does for you.

One security point: a Wi-Fi QR code contains the password in plain form, just as if you wrote it on paper. Put it only where the people you want to give access will see it, or create a guest network separate from your main one.

A contact QR code (vCard)

A card with name, company, phone, email and website, ready to save to the address book when scanned. Handy on business cards and at trade shows.

Others

You can also generate codes that open an email with subject and text filled in, start a call or an SMS, open a location on a map, or simply contain text.

How to make it scan reliably

• Contrast. Dark modules on a light background is the most reliable. Very similar colours, patterned backgrounds or an inverted code (white on black) can fail in some readers.
• Quiet zone. Leave a blank margin around the code, at least four modules wide, because readers use it to find the edges. Do not crop it.
• Size. Do not print it so small that the modules are finer than the print can reproduce. As a rough guide, a code scanned from arm's length usually works from about 2 to 3 cm per side, and should be larger the farther away it will be scanned or the more content it holds.
• Surface. Avoid placing it on a glossy material, a sharp curve or a fold.
• Test it with two or three different phones before printing a thousand copies.

Error correction level: L, M, Q or H

A QR code includes redundant data that lets it be read even when dirty or damaged. There are four levels, able to restore roughly 7% (L), 15% (M), 25% (Q) or 30% (H) of the data. Raising the level improves resilience but makes the code larger. According to Denso Wave, level M is the one most often chosen; Q or H are picked for environments where the code gets dirty, and L when there is a lot of data in a clean environment.

This correction is also what allows a logo in the centre: the logo covers part of the code and the redundancy compensates for that area. If you want to do it, use a high level and a small logo with the QR code with logo tool, and always test it.

Static or dynamic QR codes

The code this tool creates is static: it stores the content inside the picture itself, with no middleman. That means it will always work and nobody can change the destination or track you. The trade-off is that if you change the link, you have to create and print a new code. Paid "dynamic" QR codes point to an intermediary service that redirects and measures visits, but they stop working if you stop paying.

Checking a QR code you come across

You can read a QR code from an image with the QR code reader from an image, or see its content before opening it with the QR content inspector: that is how to check where it leads without visiting the site.

Sources and further reading

• Denso Wave (QRcode.com): information capacity and versions of the QR Code
• Denso Wave (QRcode.com): error correction feature
• Denso Wave (QRcode.com): standardization of the QR Code and patent
• ZXing: barcode contents format (Wi-Fi, vCard and others)
• Wikipedia: QR code (error correction levels and maximum capacity)

Figures checked on 3 October 2026.