At its core, an HTTP Hotspot WebUI is a web-based control panel served to a user's device before they are granted full internet access. When you join a public Wi-Fi network—at a coffee shop, airport, or hotel—your device sends a request to a website. The hotspot's access point or router intercepts this request. Instead of routing you to the intended site, it redirects your browser to a local web page: the WebUI. This redirection works because the initial HTTP request is unencrypted and easily manipulated, whereas HTTPS (encrypted) traffic is often blocked until authentication is complete.
The WebUI serves as the legal shield for hotspot providers. By presenting a Terms of Service (ToS) agreement and requiring explicit acceptance, the operator establishes a legal contract with the user. Furthermore, most commercial WebUIs maintain logs of connection times, MAC addresses, and visited domains (though not full URLs over HTTPS), which may be required by local data retention laws.