Choose the data type first
A QR symbol stores data, not a promise about a phone’s behavior. Plain HTTPS addresses are widely supported; Wi-Fi and contacts require recognizable formats. A scanner should show the intended action before opening a link or adding a contact. Do not shorten an unfamiliar URL merely to hide its domain.
Wi-Fi configuration
A common representation includes authentication type, SSID and password. These values are examples. Special characters, including semicolons and backslashes, need format-aware escaping; do not concatenate arbitrary input directly into fields.
WIFI:T:WPA;S:GuestNetwork;P:example-password;;Anyone with the image can read the stored password. Treat a guest-network code as sharing credentials, and regenerate it when the password changes. The simple WPA example does not describe every enterprise network using EAP authentication.
vCard contact details
Prepare a valid, line-separated vCard. Test non-ASCII characters, phone numbers and the mapping of given and family names. Scanner support for optional fields varies.
BEGIN:VCARD
VERSION:3.0
N:Example;Jane;;;
FN:Jane Example
EMAIL:[email protected]
END:VCARDAgree on the scope before including someone’s private details in a public code. A printed symbol can be copied, and its contents cannot be revoked like a database record.
Test the actual print size
Retain the quiet zone, strong contrast and sharp module edges. Scale without blurring. Vector export helps with printing but still needs validation. Longer payloads produce denser symbols. Test several phones, ordinary lighting and the distance at which readers will actually scan.
You can create a code with the MerMiko generator. Check the decoded address or payload before publication: a readable image does not establish that its contents are correct.
Sources and documentation
Source links are retained for checking dates, availability and original context.