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.

QR Code Decoder | DevTools Surf

DevTools Surf

Example: QR Code Decoder

A worked example, rendered from real sample data. Sign in to run the tool on your own input.

Input

███████ █ █ ██    ███████
█     █ ██ ██ █   █     █
█ ███ █ █ █  ██   █ ███ █
█ ███ █   █  █ ██ █ ███ █
█ ███ █ ██ █      █ ███ █
█     █       █   █     █
███████ █ █ █ █ █ ███████
         █   █ █         
█  ██████  █  ██ █  █ ███
 █  █    █     █   █████ 
█     █   █  ███  █ ██  █
 █████  █  ██     ██ ████
 █  ███  ██ █   █ ██    █
█ ████  ███  █████  █  █ 
███ ████ █ ██ ██ ██ █████
█ ████ █ ███  ██   █ ██ █
█ ███ ████    █ █████ ██ 
        ██ ███  █   █ ██ 
███████ █ ██    █ █ █   █
█     █ █   █ ███   █  ██
█ ███ █ █ █ █████████  ██
█ ███ █ █ █   ██ ██    ██
█ ███ █  █  █ █ █   █████
█     █   █   █   ███ ███
███████ ███  ██ ███  █  █

Output

═══ What this tool did ═══
✓ A QR module grid was found in your input and decoded here, bit by bit: format information, data mask, Reed-Solomon blocks and payload segments. This page runs entirely on the server that rendered it and makes no outbound network calls.
✗ No image file was scanned and no camera was used. Only the grid of modules you pasted was read.

═══ Symbol ═══
Symbol: version 2 (25×25 modules)
Error correction level: M (15% of the codewords recoverable)
Data mask pattern: 6
✓ Format information is bit-exact in at least one of its two copies.
Codewords: 44 total in 1 block — 28 data + 16 Reed-Solomon
✓ All 1 Reed-Solomon block pass the syndrome check, so the payload below is exactly what was encoded.

─── Segments ───
byte: 21 characters

═══ Decoded payload ═══
https://devtools.surf

Payload type: URL (the overwhelmingly common case — a scanner will offer to open it)
Scheme: https
Host: devtools.surf

═══ Encoding cost of this payload ═══
UTF-8 length: 21 bytes
ECC level  Smallest version  Modules  Byte capacity
---------  ----------------  -------  -------------
L (7%)     version 2         25×25    32 bytes
M (15%)    version 2         25×25    26 bytes
Q (25%)    version 3         29×29    32 bytes
H (30%)    version 3         29×29    24 bytes
ℹ Higher error correction costs modules. H recovers 30% of the codewords but needs a bigger symbol for the same text — which matters when the code has to survive a printed label or a sticker.

═══ Commands that read a real QR image ═══
  zbarimg --quiet --raw qr.png
  zbarimg --quiet -Sbinary qr.png > payload.bin
…

About QR Code Decoder

Decode a pasted QR module grid for real — version, ECC level, mask, Reed-Solomon check and payload — or explain a QR payload string. Part of the DevTools Surf developer suite. Browse more tools in the Images collection.

Use Cases

Decode a pasted QR module grid (qrencode -t ASCII output, or the generator's export) to inspect its payload before trusting it.
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.
Check whether a damaged grid still passes the Reed-Solomon syndrome check, block by block.

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.

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