QR Code Reader
Scan and decode QR codes from images instantly. Secure online QR reader for screenshots and photos. No app installation required.
Formula
Decode: locate finder patterns → sample module grid → unmask → de-interleave → Reed-Solomon correct → read segments
The decoder first finds the three corner finder patterns by their distinctive 1:1:3:1:1 run of dark and light, which fixes the symbol's position, scale and rotation. It samples the grid into modules, reads the format bits to learn the error-correction level and mask, XORs the mask away, de-interleaves the codewords, and lets Reed-Solomon repair up to roughly 7–30 percent of them depending on level. Only then are the data segments decoded back to text.
Worked Examples
Example 1: Scan WiFi QR Code
Problem:You have a screenshot of a WiFi login QR code.
Solution:Upload screenshot. Result: WIFI:S:MyNetwork;T:WPA;P:password123;; Decoded credentials you can now copy/paste.
Result:WiFi credentials extracted
Example 2: Open Website from Screenshot
Problem:A friend sent a QR code image for a website.
Solution:Upload the image. Result: https://www.example.com/promo Copy the URL and open in your browser.
Result:URL decoded
Frequently Asked Questions
How does the QR Code Reader work?
It analyzes the geometric patterns in your uploaded image to detect and decode QR (Quick Response) codes. We prioritize your browser's built-in Barcode Detection API for instant, private decoding. If that's not supported, we securely process the image via a specialized decoding service.
Which browsers decode entirely on-device?
Chromium-based browsers - Chrome, Edge, Opera and Brave - implement the BarcodeDetector API, so on those the image never leaves your machine. Firefox and Safari do not currently implement it, so those browsers fall back to the decoding service. If keeping the image local matters for a given code, open the page in a Chromium browser and the fast path is used automatically.
How can a damaged QR code still decode?
Every QR symbol carries Reed-Solomon parity codewords interleaved with the data, at one of four levels: L, M, Q and H, recovering approximately 7, 15, 25 and 30 percent of the codewords respectively. A tear, a coffee stain or a logo covering part of the pattern destroys some codewords, and the decoder rebuilds them from the parity as long as the loss stays inside that level's budget. The level was chosen when the code was created, so you cannot improve the tolerance of a code you are only scanning.
Should I scan a QR code from an unknown source?
Treat one exactly as you would an unshortened link from a stranger - the code is just an encoded string, and the danger is entirely in what it points at. Decoding an image here is safe because nothing is executed, and reading the payload as text before visiting it is the point: you see the real destination rather than trusting a printed sticker. Watch for codes physically pasted over legitimate ones on parking meters and restaurant tables, which is a common fraud.
Why does my code decode to a long redirect URL instead of the real destination?
You have scanned a dynamic QR code. Dynamic codes encode a short URL owned by a tracking service, which redirects to the true target and counts the scan on the way through. The advantage for the publisher is that the destination can be changed without reprinting; the cost for you is that the payload reveals nothing about where you will actually end up, and the code stops working entirely if the service lapses.
Is my data secure?
Yes. If your browser supports the 'BarcodeDetector' API (like Chrome on Android/Desktop), decoding happens entirely on your device. No data leaves your phone. If we use the fallback service, the image is processed in memory and immediately discarded.
Can it read blurred or damaged QR codes?
QR codes have built-in error correction (up to 30%). If the damage is within this limit, our reader can still decode it. However, extremely blurry or low-contrast images may fail.
Do I need a webcam?
No, this is an image-based reader. You can upload a screenshot or a photo you've already taken. This is perfect for scanning QR codes that appear on your own screen (screenshots).
Can it scan other barcodes?
This tool is optimized for QR codes. While the underlying technology might detect other 2D codes, standard 1D barcodes (like UPC on products) may not be recognized.
Why is the result text garbled?
If the QR code contains binary data or non-standard encoding, it might appear as random characters. Standard URLs and text will appear correctly.
Background & Theory
QR Codes use a grid of black and white squares.
Key Components:
- Finder Patterns: The three large squares in the corners that tell the scanner position and orientation.
- Alignment Patterns: Smaller squares ensuring the grid is read correctly even if distorted.
- Timing Patterns: Alternating black/white dots connecting finder patterns.
- Data Zone: The actual encoded information.
- Quiet Zone: The required white border around the code.
Error Correction Levels:
- Level L: 7% recovery
- Level M: 15% recovery
- Level Q: 25% recovery
- Level H: 30% recovery (used for codes with logos in the middle)