| Option | Description |
|---|---|
Image size | An integer in interval [10..512] defines
the width (in pixels) of the image. Depending on the amount of data
to encode, a minimum width is required.
Example 256 |
Margin (Quiet zone size) | An integer in interval [0..128] defines
how wide the quiet zone should be.
Example 4 |
Error Correction Level | QR Correction level ('L', 'M', 'Q', 'H')
Example Q |
Dark Color | Defines the color of the dark module (foreground)
Example #000000 |
Light Color | Defines the color of the light module (background)
Example #ffffff |
A QR code stores data in a grid of black and white squares, read in two dimensions rather than one. That is the key difference from a traditional barcode: a supermarket barcode encodes about 20 digits along a single axis, while a QR code uses the whole square and can hold up to roughly 4,300 characters of text or 7,000 digits.
The three large squares in the corners are position markers. They let a scanner find the code and work out its orientation, which is why a QR code reads correctly upside down or at an angle. Smaller alignment patterns keep the grid readable when the surface is curved or the photo is skewed.
QR codes use Reed–Solomon error correction, the same family of mathematics that keeps scratched CDs playable. Redundant data is woven throughout the grid so that a damaged code can still be recovered in full. The four levels trade capacity against resilience:
Higher correction means more modules for the same content, so the code becomes visually denser. If you raise the level, raise the width too or the squares become too small to scan reliably.
Width here is measured in pixels, from 10 to 512. For screens, anything from 200 pixels upward scans comfortably. For print, the rule of thumb is that the code should be at least one tenth of the scanning distance: a poster read from two meters wants a code around 20 centimeters across.
The margin — the quiet zone — matters more than people expect. Scanners need clear space around the grid to identify where the code ends. The standard calls for four modules' worth of blank margin, and codes that fail to scan when printed have often had that margin cropped away.
A QR code is not readable by eye, which makes it a convenient way to disguise a hostile link — a scam sometimes called quishing. Stickers placed over legitimate codes on parking meters and payment terminals are a recurring problem.
Check the URL your phone previews before opening it, be wary of codes in unsolicited post or email, and look closely at whether a code in a public place has been stuck over something else.
No. The code encodes your data directly, with no redirect service in between, so it works for as long as the destination does. Codes from services that shorten or track links can stop working when that service does — these cannot.
Usually, if you generate at error correction level H and keep the logo under roughly 30% of the area. Test the result carefully: the scanner treats the logo as damage, and there is no warning when you have taken away too much.
Up to about 7,000 digits, 4,300 alphanumeric characters, or 2,900 bytes at the largest version with the lowest error correction. In practice, keep it far shorter — a dense code needs a bigger print and a closer scan.
Most often the quiet zone was cropped, the code is too small for the distance, contrast is too low, or the surface is reflective. Increasing the width and restoring the margin fixes the majority of cases.
No. The code is generated in your browser, so whatever you encode — a Wi-Fi password, contact details, a private link — never leaves your device.
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