When a device joins the Wi-Fi, the network blocks its internet traffic and redirects its browser to the portal page. Once the guest accepts the terms, enters a room number and name, types a voucher code, or signs in, the gateway records the device and opens access for a set time. Phones and laptops detect the portal automatically and open the sign-in window.
Hotels, cafes, clinics, and offices use captive portals to show terms of use, control who is online, limit session length or speed, and present their own branding. In hospitality the portal can be linked to the property management system so guests log in with their booking details. It also gives the business a record that each guest accepted its usage terms.
A captive portal controls access; it does not encrypt Wi-Fi traffic or separate guests from business systems. That still requires a guest VLAN and client isolation. Portals that collect names, emails, or phone numbers fall under data protection law, so collect only what is needed and say why. Test on both iPhone and Android, since each handles portals differently. We build guest Wi-Fi with captive portals for hospitality and office networks.