QR CODES: A DEVELOPER'S GUIDE

What Are QR Codes?

QR (Quick Response) codes are two-dimensional barcodes that store data in a grid of black and white squares. Originally invented by Denso Wave in 1994 for tracking automotive parts, they became mainstream with the rise of smartphone cameras and exploded in usage during the COVID-19 pandemic as a touchless interface for menus, check-ins, and payments.

A QR code can store up to 3,000 bytes of data — enough for a long URL, a full contact card, or Wi-Fi credentials — and can be scanned even when up to 30% of the code is damaged or obscured (thanks to Reed-Solomon error correction).

The 5 Most Useful QR Code Data Types

1. URL / Website Link

The most common use case. Encode any URL and the scanner opens it immediately in the default browser. Best practices: use HTTPS URLs, consider URL shorteners for tracking analytics, and test the QR before printing.

https://armytool.site

2. Wi-Fi Credentials

The most underused QR code type. Generate a QR that connects any device to your Wi-Fi network without typing a password. The format:

WIFI:T:WPA;S:YourNetworkName;P:YourPassword;;

Print it, frame it, and put it on your desk. Guests and clients connect in one scan. Works on iOS and Android without any app.

3. vCard Contact

Encode a full contact card — name, phone, email, organisation, address, website — that gets added directly to the scanner's contacts app. Replaces business cards for digitally-inclined recipients.

4. Email

Opens a pre-addressed email draft. Useful for feedback forms, support contacts, and event RSVPs where you want to make the friction as low as possible.

mailto:hello@armytool.site?subject=Hello&body=Hi team,

5. Phone Number

Opens the phone dialler with the number pre-filled. Useful on printed materials, business cards, and event signage.

tel:+1234567890

How to Generate a QR Code

1. Open armytool.site and select QR Code Generator
2. Choose your data type from the dropdown (URL, Text, Email, Phone, Wi-Fi, vCard)
3. Enter your data in the input field — the QR code updates live as you type
4. Click Download PNG to save the QR code at full resolution

Sizing and Print Guidelines

QR codes have a minimum size requirement for reliable scanning. The general rule: the QR code should be at least 1cm × 1cm for every metre of scanning distance.

• Business cards / close-up scanning: minimum 2cm × 2cm (about 240px at 300dpi)
• Flyers and posters: 4–6cm × 4–6cm
• Storefront signage: 10cm × 10cm or larger
• Billboard: scale proportionally — for viewing at 10m, aim for 10cm minimum

Always leave a quiet zone (white border) of at least 4 modules (squares) around the QR code. This is critical — QR codes without adequate quiet zones frequently fail to scan.

Dynamic vs Static QR Codes

The QR codes generated by our tool are static — the data is encoded directly in the pattern. Changing the URL means generating a new QR code.

Dynamic QR codes encode a short redirect URL (e.g., qr.example.com/abc123) that points to your actual destination. This lets you change the destination without reprinting, and track scans with analytics. Dynamic QR codes require a paid service (Bitly, QR Code Generator Pro, etc.).

For most uses — Wi-Fi networks, contact cards, permanent links — static QR codes are better: no third-party dependency, no expiry, no subscription.

Always Test Before Printing

Before committing to a print run, test your QR code with at least two different devices and apps:

• iPhone native camera app
• Android native camera app
• A dedicated QR scanner app (Google Lens, QR & Barcode Scanner)

Test in different lighting conditions and at the minimum expected scanning distance. A QR code that fails in the field after 10,000 prints is an expensive mistake.