How to disable captive portal detection? How to remove exclamation mark on Wi-Fi or signal icon in Lollipop? When connected to the Internet, the system checks if it's in a walled garden, which is simply trying to connect to Google. If it fails, in Android 5, there'll be an exclamation mark on the WiFi icon or signal icon. 

In some situations, this is annoying. Say, in China, Google is blocked, the exclamation mark will always be there, which is meaningless.

How can I disable this check, and make the system assume, connected WiFi/mobile data is connected Internet?
It's simple. In the terminal (requires root), or in adb shell (does not require root), issue the command

settings put global captive_portal_detection_enabled 0


and reboot. It should be disabled.  The existing state can also be verified via the command

settings get global captive_portal_detection_enabled


A response of "null" indicates the global key value has not been set and Android will fall back to default of being on and performing the detection. If the detection is disabled the response of "0" will be received.

More info: Android : How to remove “captive portal” detection on android 4.2.2 and 4.3

It also works in 5.