QR Code Generator: Make Codes That Scan Every Time

A static QR code encodes your data — the URL, the WiFi credentials, the vCard text — directly into the pattern of dark and light modules. Nothing else is involved: no server, no account, no lookup. A phone camera decodes the pattern and acts on the content locally. That is why a static code can never expire. The claim that QR codes stop working after a trial period describes dynamic codes, not the format.

A dynamic code encodes a short redirect URL owned by the code service. When someone scans it, their phone visits the service's server, which forwards them to your real destination. The upside is real: you can change the destination after printing, and you get scan counts. The downside is equally real: every scan depends on that company's server staying up and your subscription staying paid. Lapsed dynamic codes are the reason so many printed codes in the wild lead to upgrade pages instead of menus.

The decision is straightforward. If the destination will not change — a homepage, a WiFi network, your contact card — use a static code and it will outlive the paper it is printed on. If you genuinely need to swap destinations after printing, you can get static-code durability by pointing the code at a short path on a domain you control and changing the redirect server-side, which keeps the dependency in your own hands instead of a third party's.

A QR code is a grid of square modules, and its size is defined by version number: version 1 is 21 by 21 modules, and each version adds four modules per side up to version 40 at 177 by 177. Your generator picks the smallest version that fits your data, which is why a short URL produces a sparse, chunky code and a long URL with tracking parameters produces a dense one. Density matters physically — more modules in the same printed area means each module is smaller and harder for a camera to resolve.

The three large squares in the corners are finder patterns; they let the decoder locate the code and determine its orientation from any angle, which is why a QR code scans upside down. Timing and alignment patterns between them establish the module grid even when the paper is curved or the photo is taken at an angle. The data itself is written in a zigzag path across the remaining modules, with a mask pattern XORed over it to break up large uniform areas that would confuse cameras.

The most useful piece of the spec to understand is Reed-Solomon error correction. Alongside your data, the code stores redundant recovery codewords, and the amount is selectable: level L can reconstruct the message with about 7 percent of the code damaged, M about 15 percent, Q about 25 percent, and H about 30 percent. This is why a scratched or partially obscured code still scans. Higher levels cost capacity — the same URL at level H needs a denser code than at level L — so the choice is a trade between resilience and module size.

Scanners need contrast between modules and background, and they are built for dark modules on a light field. Subtle brand palettes are where codes die: a mid-gray code on a beige flyer might scan on a flagship phone in good light and fail on everything else. Keep the effective contrast high, and be cautious with inverted codes — light modules on a dark background — because a meaningful share of camera apps still refuse them. Custom colors are fine as long as the module color stays clearly darker than the background; a deep navy or forest green on white scans as reliably as black, while pastels on white do not.

Size is a function of scanning distance, and the working rule is distance divided by ten. A code scanned from 30 centimeters away — a business card in hand — needs to be about 3 centimeters across; a poster meant to be scanned from 3 meters needs a code around 30 centimeters. Below roughly 2 by 2 centimeters, dense codes become unreliable for handheld scanning no matter the print quality.

Before sending anything to print, run down this list:

PNG is a raster format — a fixed grid of pixels — and it is the right choice for screens: web pages, email signatures, slide decks, and documents. Export it large; a QR code is pure geometry, so there is no penalty for generous dimensions, and downscaling is always safe while upscaling turns crisp module edges into gray blur that hurts scan rates.

SVG is vector: it describes the squares mathematically, so it renders perfectly sharp at any size, from a sticker to a trade-show wall. Print shops prefer it, it drops straight into Illustrator or InDesign workflows, and one file covers every future size need. The practical rule is SVG for anything headed to a printer or a designer, PNG for anything staying on a screen. If you must print from a PNG, size it so the code prints at 300 dots per inch or better at its final physical dimensions — a code destined to be 5 centimeters wide on paper should be at least 600 pixels wide in the file.

One format to avoid entirely for QR codes is JPEG. Its lossy compression smears the sharp module edges the decoder relies on and introduces gray transition pixels along every boundary, which effectively lowers contrast at exactly the scale that matters. A heavily compressed JPEG code often still scans on screen and then fails after printing, because the printer renders the compression artifacts faithfully. There is no size benefit worth that risk when PNG handles flat black-and-white geometry efficiently anyway.

The format works best where typing is annoying and the payoff is immediate. A WiFi code is the clearest example: the code embeds the network name, encryption type, and password in a standard format, and scanning it joins the network directly — no reading a password off a chalkboard, no support questions from guests. Printed once and framed by the register or the guest room desk, it works for years because it is static.

The inverse test matters just as much: a QR code is the wrong tool when the audience is already on a device. A code in an email, on a web page, or in a social post asks someone to point a phone at the screen they are reading — a plain link does the job better. Codes belong at the boundary between the physical world and a URL, and almost nowhere else.

Other placements that consistently justify themselves: