Wifi activity shows it's always on even though it's not on check out this screenshot i just made:



Why is the Wi-fi activity bar blue for the last 25 minutes, when my wi-fi was off for 23 minutes?

i have tasker which is set to turn off wi-fi when the phone's screen is locked. I know for sure it works because if I press the power button to turn on screen (but leave it locked) there's no wifi status icon
A credible source: AndroidPolice

tl;dr:
Google brought in an option (by default enabled!), which is a checkbox reading "Scanning always available" in WiFi -> Advanced.

The general purpose: "To improve location accuracy and for other purposes, Google and other apps may scan for nearby networks, even when Wi-Fi is off."


  To improve location accuracy


by geolocating your IP, matching it with GPS, probably seeing if you use a proxy


  for other purposes


IDK, peeking into your data maybe?


  even when Wi-Fi is off


why is there a Wi-Fi switch then?

Given, that Google has not a reputation for invading the privacy of users a bit too much, that is/was the general motive.

As said; you can turn this somewhat useless feature off (hopefully); and get some more battery life on your phone.

P.S. The fact that this option is not explicitly stated to the user when he/she begins to use the phone, and that this option is significantly hidden, concerns me.