Facebook is set to retire its Graph API version 1 on Thursday. Facebook has prepared Graph users for some time with testing tools and migration guides. On the eve of v1's retirement, Facebook posted "What to Expect on April 30" as a final reminder before the final switch to v2.
For a year now, Facebook has encouraged developers to migrate to v2, citing its enhanced login experience, which gives people more control over the information shared with apps. On Thursday, apps that have failed to migrate will lose access to any permissions that have not been approved by the new login review process. As a carrot for a v2 transition, Facebook offers a number of encouraging statistics that show v2-enabled apps request fewer permissions, enjoy higher approval rates for permissions and see higher conversion rates of new logins.
Facebook will automatically upgrade apps to the new login and v2 on Thursday. Developers can check an app's Dashboard to see if the app has been automatically updated. The HTTP header will also show the API version in use. Facebook highly recommends that developers proactively migrate to v2 to maintain control of app changes seen by users. Once an app is upgraded, users will see the new Facebook Login Dialog, new users will see an app-scoped ID, permissions will be limited to those approved by the login review, API calls will only be made for permissions approved via login review and certain permissions will cease (e.g., friends_photos).
A number of high-profile apps will be permanently affected by the transition, including Microsoft Outlook. Facebook Chat support through Outlook.com will no longer be available. Microsoft offered no fix to ended support; rather, Microsoft encourages Outlook users with chat needs to transition to its Skype chat services. For more information on the deprecation and migration, visit Facebook's FAQ page.