Apple Announces iCloud

Apple CEO Steve Jobs announced iCloud at WWDC on June 6, 2011, describing it as a replacement for MobileMe — Apple’s $99/year subscription sync service that had launched in 2008 to widespread criticism for reliability failures and data loss. Jobs called MobileMe’s execution “not our finest hour” and announced that iCloud’s core services would be free with 5 GB of storage. iCloud launched alongside iOS 5 (October 12, 2011) and OS X Lion (July 20, 2011), which were prerequisites. The service replaced the Mac-as-hub model that had defined Apple’s digital hub strategy since 2001 (the original iTunes philosophy where the Mac was the master copy of music, photos, and calendars, with devices syncing via USB cable). In iCloud’s model, the cloud was the hub: contacts, calendars, email, and purchased content would propagate to every device automatically, with no cable required. MobileMe transitioned to iCloud and was shut down on June 30, 2012.

The launch services included iCloud Backup (automatic daily over-Wi-Fi backup of iOS devices to the cloud — iOS 5 introduced over-the-air updates to eliminate the requirement for a Mac or PC entirely), iCloud email (@me.com addresses replaced @mac.com from MobileMe), Contacts and Calendars sync via CalDAV and CardDAV standards, Photo Stream (automatic sync of the last 1,000 photos taken across all iCloud-connected devices, stored for 30 days, no additional storage counted against the free 5 GB tier), iTunes in the Cloud (re-download previously purchased songs, apps, and books on new devices without local backups), and iTunes Match ($24.99/year — Apple would scan a user’s local music library, match tracks against its 20-million-song iTunes catalog, and allow downloading DRM-free 256 Kbps AAC versions of matched tracks without uploading, plus upload unmatched tracks). Documents in the Cloud allowed iWork apps (Pages, Numbers, Keynote) and third-party iOS apps to store documents in iCloud and access them from other devices.

The underlying technology challenge — synchronizing the same contact, calendar event, or document modified independently on two offline devices — was handled through conflict resolution algorithms Apple had developed from the MobileMe experience. iCloud used push notifications (Apple Push Notification Service) to wake devices when new data was available rather than polling, and leveraged CloudKit (internal) to propagate changes across devices near-instantaneously. The architecture influenced developers: third-party iOS apps could adopt iCloud storage through the Core Data with iCloud API (NSPersistentDocument in OS X), allowing user data to persist across device replacements and appear on multiple devices without users managing sync explicitly. iCloud Drive (allowing arbitrary file storage in a filesystem view, analogous to Dropbox) arrived with iOS 8 and OS X Yosemite in 2014. By 2015, iCloud had over 782 million users with 850 petabytes of stored data, having grown from approximately 150 million users at launch.