QR コード生成

Why the data type you choose matters

A QR code is just text — but scanners do something special when that text follows a recognised format. Encode a plain URL and a phone opens the browser; encode a Wi-Fi string in the right syntax and the phone offers to join the network; encode a vCard and it offers to save a contact. This generator's central feature is that it knows the exact payload format for seven different actions and builds the correct string for you, so you never have to memorise the cryptic prefixes. Pick the type, fill in the fields, and the right machine-readable text is assembled automatically.

The seven data types and the strings they produce

For email, the subject and body are URL-encoded so spaces and punctuation survive. For Wi-Fi, the T field is the security type (WPA, WEP, or nopass for open networks) and H flags a hidden SSID. The vCard block strings together name, phone, email, organisation, and website into the standard contact format that both iOS and Android recognise when scanned.

A worked example: a guest Wi-Fi code

Choose Wi-Fi, enter SSID CafeGuest, password latte2024, and leave security on WPA/WPA2. The tool builds the payload WIFI:T:WPA;S:CafeGuest;P:latte2024;H:false;;. Print that QR code and tape it to the counter: a guest scans it and their phone offers to join the network with no typing and no dictating a password across a noisy room. Notice that the password is embedded in plain text inside the code — which is exactly why a Wi-Fi QR code should only ever be used for networks you're comfortable sharing.

The customization options, and how they interact

Beyond the data type, four controls shape the final image:

• Size (128–512 px). The pixel dimensions of the rendered code. Bigger is better for print and for scanning from a distance; 256 px is a sensible screen default.
• Error correction (L, M, Q, H). How much redundancy is built in — from about 7% (L) up to 30% (H) of the code recoverable if it's damaged or partly covered. Higher correction makes the grid denser.
• Foreground color. The color of the "dark" modules.
• Background color. The color of the "light" modules and quiet zone.

The single most important interaction is between color and contrast. Scanners detect a QR code by the difference in brightness between the dark and light modules. A dark foreground on a light background is the safe, universal choice. If you pick a light foreground on a dark background (an "inverted" code), many modern phones cope but older scanners fail outright — so always test inverted codes before a print run. Likewise, two mid-tone colors with similar brightness can become unscannable even though they look fine to the eye.

Output: PNG download

The code renders onto a canvas, and the Download PNG button saves it as a raster image — ideal for embedding in documents, slides, emails, and social posts. The custom size you chose becomes the PNG's resolution, so pick a larger size up front if you intend to print, since enlarging a small PNG afterwards will blur the modules and hurt scannability.

Practical tips

• Match error correction to the medium. Level M is fine for clean screens; bump to Q or H for printed labels, packaging, or anything that might get scuffed, curved, or partially obscured.
• Keep the quiet zone. The code needs a margin of background around it; don't crop right to the edge or paste it onto a busy pattern.
• Shorter data scans easier. Long vCards and long URLs force a denser grid with smaller modules that cameras struggle to resolve from a distance. Trim optional fields or use a short link when scanning range matters.
• Test on more than one phone. Scan the actual output — at the real size, under real lighting — on both an iPhone and an Android device before committing.

Common mistakes

• Low contrast colors. The number-one cause of a pretty code that won't scan. When in doubt, go darker on the foreground and lighter on the background.
• Treating a Wi-Fi or vCard code as private. All the data — including the Wi-Fi password — is readable by anyone who decodes the image. Share accordingly.
• Forgetting the tel:/smsto: formatting. You don't need to type these prefixes yourself — selecting the Phone or SMS type adds them for you. Just enter the number and message.

A note on how it runs

The code is rendered in your browser, and the data you encode is turned into the QR pattern on your own device. To draw the code, the tool loads a small open-source QR rendering library from a public CDN the first time you generate — so a network connection is needed to fetch that script, but the content you encode (your URL, password, or contact details) is processed locally and is not uploaded to or stored on our servers.