How does QR decoding work?

The decoder converts the image to grayscale, applies an automatic threshold (Otsu's method) to separate dark and light, finds the three corner finder patterns by their 1:1:3:1:1 ratio, samples each module of the grid, removes the data mask, and reads the bitstream into characters.

Is my QR image uploaded anywhere?

No. The image is processed entirely in your browser using the HTML Canvas API. Nothing is sent to a server or third-party API, so it is safe for codes that contain Wi-Fi passwords or personal contact details.

What payload types are recognised?

It decodes the raw text of any QR code and labels common formats — URLs, WIFI: network strings, BEGIN:VCARD contacts, mailto and tel links, and geo locations — so you know what kind of data the code holds.

Why does decoding sometimes fail?

This decoder works best on clear, high-contrast, roughly straight-on images. Heavy blur, glare, extreme rotation, low resolution, or significant physical damage can prevent a clean read, in which case it reports an error rather than guessing.

Should I trust a decoded URL?

Treat decoded links with caution. A QR code can hide a malicious URL behind an innocent-looking square. Always read the full address before opening it, especially for codes from posters, emails, or unknown sources.

QR Code Decoder — Gera Tools

A QR code decoder reads the data hidden inside a Quick Response code — a URL, a Wi-Fi login, a contact card, or plain text. This tool does it without a camera and without uploading anything: drop an image of a QR code and it is decoded right in your browser.

How it works

QR decoding is a small computer-vision pipeline:

Load and grayscale. The image is drawn onto an HTML canvas and each pixel reduced to a single brightness value.
Binarise. Otsu’s method picks the brightness threshold that best separates dark modules from light ones, turning the image into pure black and white.
Find the code. The three large corner squares — the finder patterns — are located by their characteristic 1:1:3:1:1 run of dark and light, which fixes the grid’s position and module size.
Sample the grid. Each module’s centre is read as a single bit, reconstructing the matrix.
Unmask and read. The format bits reveal which of the eight data masks was applied; reversing it and walking the modules in QR’s zig-zag order yields the bitstream, which is parsed into numeric, alphanumeric, or byte (UTF-8) characters.

Tips and notes

For the cleanest read, use a sharp, high-contrast image taken straight on. A screenshot of an on-screen QR works perfectly.
The result is labelled by type. A WIFI: string, for example, is flagged as a Wi-Fi network so you can see at a glance what the code carries.
Because everything is local, this is a safe way to inspect a QR code’s destination before trusting it — decode first, then decide whether to visit the link.
Very dense codes (high versions), heavy rotation, or damage may not decode; the tool tells you honestly instead of returning a wrong guess.