Apple announced a raft of new developer features for the forthcoming iOS 8 at its Worldwide Developers Conference, with an updated SDK including more than 4,000 new APIs.

Referring to the SDK, Apple CEO Tim Cook said: “This release is the biggest release since the launch of the App Store and it will give developers the capabilities and tools to make things they haven’t dreamed of and to push to a whole new level.”

Extensibility is one of the major new features, enabling apps to extend and communicate with each other via iOS while remaining contained in their own sandbox.

This could enable the sharing of content from the Safari browser to the Pinterest app, the use of photo filters on images contained outside an app, or for the Bing translation functionality to be applied to web pages within Safari, for example.

The new HomeKit API allows connected device apps to be integrated with iOS so that in-home devices can be controlled via Apple devices, while the HealthKit API provides a way for data from third-party health apps data to be made available in a single place.

Developers will also be able to apply Apple’s TouchID fingerprint technology to apps for logins and to access user data. In addition, developers can define widgets for their apps that appear in the Notification Centre, allowing limited functionality without the need to fully open an app.

Craig Federighi, Apple’s senior vice president of software engineering, said Swift, a new programming language for developers working with iOS, “enables a level of dynamics and interactivity in development that we’ve never seen before”. Code created using Swift can sit alongside Objective-C and C code within the same app.

A beta of TestFlight was also announced, which allows developers to invite users to test their apps for free before they are released to the App Store.

The company also introduced a new graphics technology called Metal, which enables iOS games to access more of the power available from Apple’s A7 processor.

The betas of iOS 8 and Swift are available immediately for iOS Developer Program members with the technology due to be released commercially in the autumn.

While discussing the new developer tools, Tim Cook announced some improvements to the App Store, which now has 1.2 million titles available with 75 billion downloads having been made by the 300 million weekly visitors.

“We are really investing a tonne in the App Store. What we want to do is make the App Store even better,” Cook said.

App bundles, where multiple apps can be bought at a discounted price, will be possible with iOS 8, while developers can add short videos to their app description page to show off the most interesting features of their products.

In addition, a new family sharing option allows shared access to the same credit card for App Store purchases. Purchases made by children require the cardholder’s permission, which is flagged through a notification to the cardholder’s iOS device.