SSID

An SSID (Service Set Identifier) is a name for identifying a Wi-Fi network. The network name shown when you open the Wi-Fi settings on a smartphone or computer is the SSID. It consists of up to 32 alphanumeric characters, and when several Wi-Fi networks exist in the same place, it serves to distinguish which network to connect to.

When sharing Wi-Fi connection information with a QR code, three pieces of information are stored in the QR code: the SSID, the password, and the encryption method (WPA/WPA2/WPA3). When you scan the QR code with a smartphone, this information is entered into the Wi-Fi settings automatically, saving the effort of typing in the password by hand. When cafes and hotels post a QR code saying "Wi-Fi here", they are using this mechanism.

From a security standpoint, it is also possible to set the SSID to hidden (stealth mode), but this is not a fundamental security measure. Even if the SSID is hidden, it can be found out by intercepting the communication. Real security should be ensured with a strong password and an encryption method such as WPA3.