How many bindings will IIS 7.5 support on one web site ?

To make sure my question is understand correctly.

  • I know i can put multiple website on the same server.
  • I know i can put multiple website on the same IP
  • I know i can put multiple binding on the same website

My questions is, it's there a limit of binding on the same web site.

Supose i get something like

  • www.serverfault.com
  • serverfault.com
  • m.serverfault.com
  • a.serverfault.com
  • b.serverfault.com etc..

On the same web site binding ....


3 Answers 3


If you are using kernel-mode authentication, the limit is 64 bindings (Confirmed with Microsoft). I have tested it. It fails (401.2 error) if I add 65 or more bindings.

I am not aware of any limitation if you use user-mode authentication.

More information: IIS binding limit (401.2 Windows Authentication error)


In theory the maximum number of bindings per site is 65535 (the total number of ports available, period), minus, of course, any ports otherwise in use on the system (i.e. 25, 110, 3389, etc).

Now, what you'd need with 65k ports bound to the same site is beyond me. Mailq's reference to the How Many Sites question may be more what you want to know.

  • 3
    @Driftpesant, why it's limited by the number of port ? It's suppose to be only a validation on the header of the HTTP request no ? Dec 16, 2011 at 14:46
  • In this case @CédricBoivin is right. Binding in IIS is not what you normally expect by the word "binding". MS is stupid in this case.
    – mailq
    Dec 16, 2011 at 18:32
  • Actually no - binding in IIS means exactly this. It is just - due to http - not as primitive / limited as a pure port binding.
    – TomTom
    Nov 26, 2013 at 18:28

I'd say that the limit to bindings should practically be dependant on how large applicationHost.config can be: MS reference

  • This is only true for IIS6 and older versions (in which there was an actual limit of 1024 endpoints bound). In IIS 7.0 and above, site bindings are stored in applicationHost.config Jan 31, 2014 at 15:41

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