What is a captive portal?
Definition
A captive portal is the branded sign-in page a guest sees when they first join a public WiFi network. The network holds the device until the guest completes an action, such as social login, email, SMS, a voucher or SSO, accepting terms, or opting in to marketing, then grants internet access.
Captive portal explained
Under the page is a network mechanism. An unauthenticated device can reach only a walled garden: a short list of pre-approved domains the portal and its login providers need. Any other request is intercepted and redirected to the portal URL, often through DNS redirection. Once the guest signs in, RADIUS or the controller releases the device onto the guest VLAN.
Phones and laptops look for portals on their own. iOS, Android, Windows and macOS send probe requests on joining a network and open a mini browser when they detect a portal. If the walled garden blocks those probes, the portal never appears, which is the most common cause of guest WiFi connection failures.
For the venue, the captive portal is where data and consent are captured. GDPR requires a clear privacy notice and explicit consent per sign-up, with consent logs kept for audit. The splash page is the design layer the guest sees; the captive portal is the whole mechanism around it. Designed well, it is the main source of first-party data a physical venue has.
Need more than a definition?
Talk to our team about how Purple combines guest WiFi, captive portals, RADIUS, and analytics into a single platform that runs on the access points you already own.