What is it?

OpenID is a free, universal digital identity across the Internet. It can be considered similar to a Single Sign On (SSO) login, in terms of enterprise applications.

Why is it required?

• Eliminates the need for maintaining multiple User IDs across websites
• OpenID is non-proprietary and completely free to use
• Ability to choose the OpenID provider, that you trust
• Reduces the account management effort and cost, for developers and business

How does it work?

Once you sign up for an OpenID, you get an URI as the OpenID login name.  This URI will vary depending on your OpenID provider.  For example, if your login name is ‘thoughts’ with MyOpenID, then the URI might be something like ‘thoughts.myopenid.com’.

You can use these credentials wherever OpenID is accepted.  For example, following is how MyChores let their users use their OpenID, for authentication purposes.

Where can I get an OpenID?

There are many providers in the space, who manages your OpenID creation and usage.  Following is the list, which may grow soon:

ClaimID

myID.net

MyOpenID.com

myvidoop.com

Verisign Labs

You already have an OpenID, if you maintain an account with any of the following services.

 
Since the support for OpenID is spreading fast, the list might grow very soon.  Refer to the original list of OpenID services, for accurate results.

For Developers

OpenID is a free, user-centric digital identity based on well known standards like HTTP, URI etc. and leverages the usage of various IDs that people create over various services across the web. This eases the account management effort and offers users a seamless browsing experience.

Couple of guides to get started with OpenID:

http://www.plaxo.com/api/openid_recipe

http://www.intertwingly.net/blog/2007/01/03/OpenID-for-non-SuperUsers

Further, the OpenID community has developed lots of libraries and documentation, for OpenID usage. All these can be found here.

Conclusion

OpenID is still in adoption phase. Heavyweights like Sun, AOL etc. have started to adopt OpenID, which is a really good sign. Currently, there are about 160 million OpenID URIs, with 10000 sites accepting them for logins.