About QR Code Scanner

Simulate QR code scanning and decode data with error correction. Part of the DevTools Surf developer suite. Browse more tools in the Images collection.

Use Cases

• Decode a QR code from a screenshot to inspect its embedded URL before clicking.
• Test whether a QR code at a given size and error correction level decodes reliably.
• Validate that a dynamically generated QR code contains the correct payload.
• Simulate scan outcomes for QR codes with partial damage to verify error correction coverage.

Tips

• QR code error correction levels L/M/Q/H allow 7/15/25/30% of the code to be damaged while still decoding — use H when embedding a logo over the center.
• Verify decoded URLs before following them: QR codes are a common phishing vector since the destination is not visible before scanning.
• For long URLs, test the generated QR at the smallest intended display size — high data density at small print sizes degrades scan reliability.

Fun Facts

• QR codes were invented by Masahiro Hara at Denso Wave in 1994, originally to track automotive parts on assembly lines. Denso Wave never enforced the patent, making QR royalty-free.
• A QR code can encode up to 4,296 alphanumeric characters or 2,953 bytes of binary data in the highest-density version (Version 40, 177x177 modules).
• QR code usage surged 750% in the US between 2018 and 2022, driven largely by contactless menus during the COVID-19 pandemic.

FAQ

What types of data can a QR code encode?

URLs, plain text, vCards (contacts), WiFi credentials, calendar events, email addresses, phone numbers, and arbitrary binary data. Each data type has a mode optimized for encoding efficiency.

Why does my QR code not scan?

Common causes: insufficient contrast (need at least 3:1 ratio), quiet zone not preserved (requires 4-module white border), print resolution too low (need minimum 300 DPI for small codes), or data density too high for the target display size.