A captive portal is a web page accessed with a web browser that is displayed to newly connected users of a Wi-Fi or wired network before they are granted broader access to network resources. Captive portals are commonly used to present a landing or log-in page which may require authentication, payment, acceptance of an end-user license agreement, acceptable use policy, survey completion, or other valid credentials that both the host and user agree to adhere by. Captive portals are used for a broad range of mobile and pedestrian broadband services – including cable and commercially provided Wi-Fi and home hotspots. A captive portal can also be used to provide access to enterprise or residential wired networks, such as apartment houses, hotel rooms, and business centers.

The captive portal is presented to the client and is stored either at the gateway or on a web server hosting the web page. Depending on the feature set of the gateway, websites or TCP ports can be white-listed so that the user would not have to interact with the captive portal in order to use them. The MAC address of attached clients can also be used to bypass the login process for specified devices.

WISPr refers to this web browser-based authentication method as the Universal Access Method (UAM).