regarding logging to some web-site using fb,gmail account

i want to know how the web-sites are allowing new user to lo开发者_StackOverflowg on to their web-site using gmail,fb or yahoo account.Does these sites gives their logging API open to all to use by anyone .

1.Do they have some collaboration with these sites to access their database ??

2.Does these sites ask for some money to access the information of the user ??

Take a look at open ID, (in use here) and Facebook Connect. In my opinion, FB connect leads to a better user experience, as open ID is (last I checked) sort of wonky to use if you're not ready for it (you get kicked off the the site that verifies your open ID, then come back).

There are a number of open ID providers, including yahoo & google.

Neither require a massive deal with a massive company - they're all free services.

Google, Facebook, Yahoo etc Are all Open ID providers, which means you integrate all of them in your website with relative ease. You can check it here. There are a variety of libraries that wrap around the API with your language of choice.

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