QR code content

A phone that scans a QR code acts on its text when it recognizes a format: it joins a Wi-Fi network, adds a contact, opens a mail. QRCodePayload builds these texts; pass the result to QRCode.Create:

var payload = QRCodePayload.Wifi("Guests", "correct horse battery staple", WifiAuthentication.WPA);
var qrCode = QRCode.Create(payload, ErrorCorrectionLevel.Q);

// A phone that scans it offers to join the network
var png = qrCode.ToPng(new QRCodePngOptions { ModuleSize = 4 });

Formats

// WiFi
var wifi = QRCodePayload.Wifi("MyNetwork", "password123", WifiAuthentication.WPA);
Assert.Equal("WIFI:T:WPA;S:MyNetwork;P:password123;;", wifi);

// vCard
var vcard = QRCodePayload.VCard("Doe", "John", phone: "+1234567890", email: "john@example.com");
Assert.StartsWith("BEGIN:VCARD\r\nVERSION:3.0\r\nN:Doe;John;;;\r\nFN:John Doe\r\n", vcard);

// MeCard (compact contact format)
var mecard = QRCodePayload.MeCard("Doe", "John", phone: "+1234567890");
Assert.Equal("MECARD:N:Doe,John;TEL:+1234567890;;", mecard);

// Email
var email = QRCodePayload.Email("test@example.com", subject: "Hello");
Assert.Equal("mailto:test@example.com?subject=Hello", email);

// Phone
var phone = QRCodePayload.Phone("+1234567890");
Assert.Equal("tel:+1234567890", phone);

// SMS
var sms = QRCodePayload.Sms("+1234567890", "Hello!");
Assert.Equal("smsto:+1234567890:Hello!", sms);

// Geolocation
var geo = QRCodePayload.Geolocation(48.8566, 2.3522);
Assert.Equal("geo:48.8566,2.3522", geo);

// Calendar event
var evt = QRCodePayload.CalendarEvent("Meeting",
    new DateTime(2025, 6, 15, 14, 0, 0, DateTimeKind.Utc),
    new DateTime(2025, 6, 15, 15, 0, 0, DateTimeKind.Utc),
    location: "Room 42");
Assert.Contains("DTSTART:20250615T140000Z\r\n", evt);

// OTP Auth (2FA setup)
var otp = QRCodePayload.OneTimePassword(OneTimePasswordType.Totp,
    "JBSWY3DPEHPK3PXP", "user@example.com", issuer: "MyApp");
Assert.Equal("otpauth://totp/MyApp:user%40example.com?secret=JBSWY3DPEHPK3PXP&issuer=MyApp", otp);

// Bitcoin payment
var btc = QRCodePayload.Bitcoin("1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa", amount: 0.05m);
Assert.Equal("bitcoin:1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa?amount=0.05", btc);

// SEPA payment (EPC QR)
var sepa = QRCodePayload.SepaPayment("Example", "DE00000000000000000000", 12.50m,
    remittanceText: "Donation");
Assert.StartsWith("BCD\n002\n1\nSCT\n", sepa);

• The values are escaped for their format: a ; or a line feed in a name cannot change the fields of a vCard, and a ? in an email address cannot add parameters to the mailto: link.

• SepaPayment follows the limits of the format (EPC069-12):

  • The amount is from 0.01 to 999,999,999.99, in whole cents. An amount such as 0.015m throws an ArgumentOutOfRangeException instead of being rounded; 10.000m is accepted.
  • The beneficiary name has 70 characters at most, and the remittance is either a structured reference or a text.
  • The whole payload is 331 bytes at most in UTF-8, or the method throws an ArgumentException. The field limits count characters, but a character outside ASCII, such as é, takes several bytes.
  • A value that contains a control character, which the format cannot escape, throws an ArgumentException instead of shifting the fields.
  • The payload ends with the last value you set: the empty fields after it are left out.

  The guidelines also limit the symbol to version 13 with error correction level M: keep the default level of QRCode.Create. A payload of 331 bytes fits in version 13 at level M.

• OneTimePassword rejects a URI that an authenticator app cannot use, following the Key URI format:

  • The digits are 6, 7 or 8. Google Authenticator documents only 6 and 8.
  • A TOTP period is greater than 0. The period is ignored for HOTP.
  • A HOTP counter is required and is 0 or more: a missing counter throws an ArgumentException, and a negative one an ArgumentOutOfRangeException. The counter is ignored for TOTP.

• A payload is plain text: you can also write your own, such as a URL.