On the surface, this has striking similarities to Facebook Connect, the Facebook version that allows users to access 3rd party websites using a Facebook account, as well as import their Facebook information and friends. So how does Sign in with Twitter work, and how does it compare to Facebook Connect?
How To Log In with Applications that Use FB Connect or Twitter Sign In
Sign in with Twitter: Sign in with Twitter is a three-step process:
1. Request to sign in via Twitter
2. Log in to Twitter
3. Authorize the application or website to let you log in via Twitter
For the user who is logging in, it is in fact dead simple. If you are logged into Twitter, the only thing you really have to do is authorize the website to let you log in via Twitter. After that, OAuth takes over, which basically allows the website or application to access information like your friends, followers, and bio. And like many Twitter applications, it also allows you to send out and receive tweets via Sign in with Twitter.
Because Twitter doesn't have the same detailed information that Facebook has (i.e. relationship status, colleges attended, news feed updates, etc.), Sign in with Twitter is not able to bring in as much information.
Facebook Connect: Facebook Connect is just as simple for the user - you request to log in to a website via Facebook and, if you're logged in, it will ask you to authorize the website to connect to your Facebook.
The real difference for the user is the information being imported and exported. With Facebook Connect, information on location, gender, and favorites can be imported, making filling out a profile on a 3rd party website almost unnecessary. It also allows users to send stories to his or her wall and news feed. With Sign in with Twitter, the strength is in the user's ability to send and read tweets, as well as information on friends and followers.
Technology and Implementation: Twitter vs. Facebook
Technologically, Facebook Connect and Sign in with Twitter are definitely different - the way the developer implements it as well as how users connect to another website are done via different methods, even if the result is very much the same.
Sign in with Twitter uses OAuth, the system which already allows users to log into Twitter applications without having to type in their username and password. Sign in with Twitter is really a small addition to OAuth, but has big implications. Developing for Twitter is generally known to be simple, mostly because the Twitter platform itself is simple, when compared to others like MySpace or Facebook.
This could convince more time-strapped developers to choose Sign in with Twitter over Facebook Connect. Twitter is also a more open platform (information is not limited to friends unless you specifically make your profile private), meaning things can go more viral and information is not as walled in as it is on Facebook.
Is Sign in with Twitter a Facebook Connect competitor?
If the only thing you care about is allowing users to log into your website, then the answer is yes. If you want to have users promote your website by sending out tweets or news feed items, then the answer is yes. But for many developers, who are looking to leverage Facebook's detailed personal information for a more personalized experience, the answer is a no.
For most people, Twitter followers are not the same as Facebook friends - Facebook friends are closer, more personal connections. This makes seeing their updates and information on a 3rd party website more compelling than perhaps Twitter. Sign in with Twitter, however, may be better suited for more "open" experiences, i.e. sharing links or meeting new people in your industry. Facebook Connect and Sign in with Twitter have different applications and purposes once you get past the log-in screen.
However, Sign in with Twitter is still a win for users and developers - it's easy to use, easy to implement, and gives everyone another alternative to Facebook Connect, MySpace ID, Google Friend Connect, and other platforms with similar functionality.