Often now, when I connect to a public or corporate Wifi access point, on connection a browser pops up and directs me to a website to log in.

Presumably this is an OS function, which is triggered from the AP? If so:

  • How is this done? does the AP send a specific message in a post connection packet, including the destination address?

  • What is this process called (if anything)?

  • What OS versions support this process?

(Sorry for posting multiple small questions but they are all intrinsically linked)

  • Unfortunately, questions about networks you do not directly control are off-topic here, as are questions about hosts, OSes, and protocols above OSI layer-4.
    – Ron Maupin
    Commented Sep 11, 2017 at 11:59
  • oh. ok. strange that a completely network based question is off topic in a completely network based stack. Commented Sep 11, 2017 at 12:24
  • Please read the help center, as you should for any SE site before you ask a question there.
    – Ron Maupin
    Commented Sep 11, 2017 at 12:26
  • You know as well as I do that nobody reads those!!! I got a correct answer anyway, hopefully PHoSawyer gets his points. Commented Sep 11, 2017 at 12:28

1 Answer 1


The general process is called a "Captive Portal". It is essentially a redirect. You open your browser and try to goto a website. The AP controller redirects you (HTTP 301 I believe) to their site to confirm T&C's or to login.

Once you are logged in (or just accepted T&C's) your ID is normally your MAC address so when the AP see's your MAC it allows you onto the AP with whatever privileges your user has.

I've noticed firefox has a background process that calls home, if it can't then it lets you know you are in a hotspot/captive portal scenario which is quite helpful. iPhones have a similar thing where they pop up an announcement specifying you have to logon to the hotspot.

  • OK that's interesting so its actually a client-side thing and isnt actively called for by the AP? I use Chrome mostly and this pops up almost immediately on connecting. Commented Sep 11, 2017 at 11:19
  • All the clever stuff is done on the AAA (Authentication, Authorization, Accounting) Server. The quick background check with the pop-up happens inside the browser.
    – boopzz
    Commented Sep 11, 2017 at 11:23

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