QR code decoding, step by step

QR Visualizer is a browser-based QR code decoding visualizer. It shows how a QR decoder moves from a real image to the final decoded payload while keeping each stage visible and explainable.

1. Image binarization

The decoder first converts the image into a black-and-white representation so QR modules can be analyzed consistently even when lighting varies.

2. Finder patterns, rotation, and alignment

The visualizer highlights the QR finder patterns, corrects orientation, searches for alignment information, and shows the timing geometry used to understand the code structure.

3. Perspective correction and grid sampling

Once the QR geometry is known, the image is mapped onto a square module grid. Each QR cell is sampled so later stages can operate on the rendered module matrix instead of the original photo.

4. Format information and masks

QR codes store format information in two physical copies. QR Visualizer shows how those bits are extracted, unmasked with the fixed format mask, checked for errors, and resolved into error-correction level and mask pattern metadata.

5. Data extraction and error correction

After the mask pattern is known, the decoder follows the QR data path, extracts codewords, separates message bytes from error-correction bytes, and explains how recoverable damage can be corrected.

6. Final payload

The final stage presents the decoded text or URL. If the payload is a valid web link, QR Visualizer can open it directly from the browser.

Privacy

Uploaded QR images and camera captures are processed locally in the browser. The app does not upload images for decoding.