A captive portal is a web page that requires users to authenticate or accept terms of service before they can access the internet through a wireless access point. A captive portal can be used to control who can use the wireless network, limit the bandwidth or time of usage, or display advertisements or information. A captive portal is a common feature of public wireless networks, such as those in hotels, airports, cafes, or libraries. A captive portal can prevent unauthorized or malicious users from accessing the network or consuming network resources.
References: Public Wireless Access Points Definition | Law Insider