QR Code encoding explained
A QR Code does not store an image or an icon, it stores plain text formatted according to a convention the reader app knows how to interpret. Understanding that text behind the checkerboard pattern explains why some codes open Wi-Fi settings automatically and others just open a browser.
The semicolon in the password gets a backslash right before it; without that escape, the reader would treat the password as ending at "S3nh4" and break the next field.
The phone number becomes a TEL;VALUE=uri:tel: field with the mandatory tel: prefix, and a website typed without a protocol gets https:// added automatically before becoming the URL field.
The recommendation steps up as soon as the logo passes 14% coverage (becomes Q) and again past 20% (becomes H), because each extra band of covered area needs more redundant data to reconstruct what the logo is hiding.
Yes. In addition to text, URL, Wi-Fi, email, phone and SMS, it generates vCard 4.0 contacts and iCalendar/VEVENT events for import by compatible apps.
There are 4 levels defined by the ISO/IEC 18004 standard, each recovering a larger slice of damaged data: L around 7%, M around 15%, Q around 25%, and H around 30%. A higher level makes the code more resistant to smudges, folds, and an overlaid logo, but in exchange it uses more modules in the same space, making the pattern visually denser.
Shrinking the file size compresses neighboring modules until a camera can no longer tell them apart, and that hits hardest exactly around the logo, which already depends on error correction to be reconstructed. Exporting at a larger resolution (1024px or more) and using level H whenever there is a logo cuts down that risk.
Yes, as long as the phone has QR scanning built into the system camera (standard since iOS 11 and Android 8), because the WIFI:T:...;S:...;P:...;; format is not proprietary to any manufacturer, it is a convention both systems adopted independently to auto-fill the connection screen.
Yes, and the practical limit depends on the version and error correction level chosen: the more text, the larger the code version (more modules), which makes the pattern harder to read on small screens. This tool rejects payloads longer than 1800 characters specifically to avoid codes too dense to scan reliably in everyday use.
The QR Code is generated in your browser. Content, Wi-Fi, contact and event data are not sent to the server.