SAN FRANCISCO, CA—After months of rumors and speculation, Apple took the wraps off of iOS 8 today at the opening keynote of its 2014 Worldwide Developers Conference. The latest version of Apple's iPhone and iPad operating system retains and refines the "flattened" user interface introduced in iOS 7 last year while introducing new features and APIs.

Apple has revamped Notifications Center in iOS 8 so users can respond to messages without leaving the app they are in. The function will work for apps like Messages and Calendar, and items can also be answered from the lock screen.

The keyboard gets an update with QuickType, a context-aware set of suggestions for words to include in messages. The suggestions are personalized and will differ from contact to contact, and Apple reassured users that the keystrokes and learning are all conducted in the device and do not need to be sent to Apple's servers for processing.

The Continuity features in OS X will likewise be featured in iOS so users can throw calls, documents, and messages between their iOS and OS X devices. Group messages in iOS will now be organized as threads with titles where participants can be added or removed. Locations can be shared in iOS 8 message threads, and users can also record snippets of audio and swipe up from the recording field to send them. Apple is also adding the ability to mute individual conversations, and media in conversations is now curated together in a "details" pane. iCloud Drive will be integrated with iOS 8, allowing users to see files stored in iCloud from application in a single pane.

Apple introduced a new API in iOS named Healthkit that can aggregate information about your weight, exercise levels, and medication schedules to help you manage all of it. Healthkit can collect data from external third-party apps from companies like Nike, and from fitness gadgets by extension. The door is obviously open for Apple to introduce its own health tracking gadget later on.

Not only can Healthkit curate this information, it can pass it on with the user's permission. For instance, if the user takes a blood pressure reading that registers higher than normal, Healthkit can pass that information along to the user's doctor.

Family sharing has received some updates in iOS 8. Calendars, photos, reminders, and photo streams can all be shared between family phones, as well as Find My Friends position, with permission. Up to six family members who share one credit card on their accounts can also mutually share purchased items like movies, apps, books, and music.

Photos will now back up automatically to iCloud so that all photos are available on every device (however, Photo Stream has always had a 1,000 photo limit, so it's unclear whether the new iCloud integration will have to play along with that limit). Photos can also now be searched by location, date, and album, and the app will get new editing tools for lighting, color, auto-straightening, and cropping. Favoriting photos on one device will make them appear in a special "favorites" album on other devices.

Along with photo sync, Apple is introducing new iCloud storage pricing. The 5GB tier will remain free, with 20GB costing $0.99/month and 200GB at $3.99 per month.

Updates to Siri include Shazam song recognition and streaming voice recognition that will show what Siri is transcribing as the user talks, rather than compiling it in one fell swoop once they stop recording. Apple has also added to Siri 22 new dictation languages.

Mail in iOS will receive some tweaks: messages can be marked as read with a single gesture, and the app will gain context-aware shortcuts, like adding events to a calendar. Users can also now move a draft message window aside to navigate the rest of the inbox, rather than having to save the draft and re-open it later. Mail will also have a feature called "VIP threads" that lets users get notifications on a per-thread basis.

The new version of Spotlight in iOS will now include results for things that are not on the user's phone, including news or apps available in the App Store that have not yet been bought or downloaded.

The iPad version of Safari will gain some previously iPhone-exclusive features like the bird's-eye tab view and Safari sidebar.

To address Enterprise customers, Apple has set up a new system that installs a user profile on a device before it is sent to the customer so that IT will not have to deal with that extra step. Third-party enterprise document providers will also now integrate with iCloud, though Apple did not specify which apps or companies.

As for the App Store, Apple plans to add an Explore tab to help users find new apps, as well as top trending searches and continuous scrolling in search. Users will soon be able to buy apps in bundles at discounted prices, and soon developers will be able to include videos in their app listings to demonstrate what their apps do. Devs will be able to invite users to beta-test apps for free using TestFlight.

For Xcode, Apple has created a new programming language called Swift, which it calls "Objective-C without the baggage of C." Apple states that Swift is 3.9 times faster than Python at complex object sorting, and also fast with RC4 encryption. Apple states that Swift can sit next to C and Obj-C code in the same application, and Xcode will show live demos of what Swift code is doing as it's added in a separate pane.

More significantly, Apple is loosening some of the restrictions on third-party applications to allow them to interact with each other more easily. In older versions of iOS, only third-party apps and services "blessed" by Apple (e.g. Twitter, Facebook) could easily upload and share pictures and other files from most apps via the Share menu. In iOS 8, people who want to post a picture directly from the camera roll to Google+ should be able to, as will anyone who wants to upload a Word document from Office Mobile to Dropbox. Apps will presumably need to be updated to support the new feature, but iOS developers are typically quick to jump on board when it comes to features like these.

Developers will also get an API to add widgets to Notifications Center, system-wide third-party keyboards (hello, Swype), and an API for the TouchID sensor. Apps can use TouchID for logins and to organize user data, but developers will not get direct access to the fingerprint data itself. Apple revealed that it is developing a network protocol, HomeKit, to allow users to control things like garage doors and lights from their iOS devices.

Apple revealed the new CloudKit with iOS 8, a "free with limits" programming model that lets developers access iCloud authentication, storage, and search with 1PB of assets and a 10TB database. Developers will also get access to Metal, a new 3D graphics API designed to work with the A7 processor that reduces the overhead typically seen from using OpenGL. Another tool, SceneKit, will allow users to render games with built-in physics and particle engines.

The iOS 8 beta is available to WWDC developers starting today, with the official release coming in the fall.

Apple's WWDC keynote is ongoing. We'll continue to update this post with more details as they're announced. For up-to-the-minute info, you can follow our liveblog.