Many times I get asked by developers, "should I build for Facebook or mobile?", and the answer is, both. It's not a question of one or the other. Mobile apps, just like apps on Facebook.com, can benefit from an audience of more than 900 million users, 500 million of whom are active Facebook mobile users.

Regardless if an app lives on a mobile platform, like iOS or Android, or on Facebook.com, it can plug into Facebook and grow through News Feed, timeline, Requests, Bookmarks, Search, and now the App Center. Last month, Facebook drove people to iOS apps 134 million times, and to the Apple App Store 83 million times.

By enabling people to log into their apps with Facebook, mobile developers can reach a wider audience, and keep people coming back.

Go from solo to social

It all starts with Facebook for login, which is how mobile developers can turn one user into many.

Wooga's game, Diamond Dash is available on Facebook.com, and as an iPhone app. People can log into the iPhone app with their Facebook account, find their friends, and share back to Facebook.

Once a mobile app integrates with Facebook, people can log into the app in one click, without needing to remember a separate user name and password. Once the mobile app is connected to their Facebook account, users can find friends and share activity (such as scores and achievements) back to Facebook. Additionally, a bookmark will be added on the Facebook mobile app, so it's easy to re-engage.

For mobile developers, using Facebook for login improves conversion by providing an easy registration process, increases engagement by making it possible for people to connect with friends, and offers distribution through Facebook.

Examples of top iPhone apps integrated with Facebook include: Texas HoldEm Poker, Slotomania , Bejeweled Blitz, Diamond Dash, Words With Friends, Draw Something, Nike+ Running, Pinterest, Goodreads, Pose, Foodspotting, DoubleDown Casino, and Stitcher Radio.

Facebook complements a mobile strategy

SongPop

SongPop, a "Name That Tune"-style game by FreshPlanet, is available as a Facebook-connected app on Facebook.com, iPhone and Android, and 65% of mobile users login with Facebook (vs. email).

The SongPop iPhone app

SongPop on Facebook.com

The app has become one of the fastest growing social games, with 3.9 million monthly active Facebook users across web and mobile.

Songza

Another music app built with Facebook, Songza, recently became the #1 free music app on the iPhone and iPad. During this time, the number of Facebook-connected users grew from 7,000 daily actives to more than than 120,000.

Songza users are given the option to log into the iPhone and iPad apps with their Facebook account or email address, and more than double the percentage of users sign in with Facebook.

Not only do the majority of people log into Songza with Facebook, but those users share the experience with friends, driving viral growth to the app. In May, each active Facebook-connected user generated more than one referral visit.

Social growth and discovery: Songza can be found through Facebook in the App Center, bookmarks, timeline, and more.

The social games ecosystem is growing

More than 230 million people play games on Facebook.com every month. And, more than 130 games on Facebook have more than 1 million monthly active users each, from King.com (52.3M+ users), to Peak Games (18M+ users), Rovio (17.3M+ users), Playtika (7.2M+ users), Halfbrick (6M+ users), and Kixeye (4.7M+ users).

We'll continue to build tools that benefit mobile, web, and cross platform developers, to make it easier for people to find social apps, and share them with their friends, wherever they are.