You see a mysterious message in a window on your Mac’s screen when trying to connect to Wi-Fi: “Paused” with a big blue Pause button. Additional text reads, “Your device has been paused.” At the bottom of the window, you see a domain, captive.apple.com, and a Cancel button. A similar window appears in a view on an iPad or iPhone. The message is clear: you can’t access the internet via this connection.
What’s creating this dialog, and why does captive.apple.com appear on a Mac in a window that shows it? A Wi-Fi router has produced the message, and Apple’s not involved except in displaying it.
Several years ago, Apple added a clever method (first to Macs and later to iPhones and iPads) to let them work effectively at Wi-Fi hotspots that required accessing a portal page. Those hotspot portals hijack DNS (domain naming system), the system that turns human-readable domain names (like http://www.macworld.com) into computer-manageable Internet Protocol (IP) addresses (like 192.0.66.208).
Read more at Macworld.com