Apple's beta testing program for OS X 10.10 was initiated last July, offering up to 1 million users an early version of the latest Yosemite build prior to the official release. This program hopes to point out bugs on the pre-launch builds so that the final version would be made stable. Now, Apple is expanding its public beta program to iOS 8.3. 

Users and developers can sign up for the program on a dedicated Apple site. After signing up, interested developers can enroll into the iOS beta program. Users can then install the beta software after downloading, and report any bugs, issues, or inconsistencies directly to Apple using the built-in Feedback Assistant app. 

iOS 8.3 was seeded to developers on Feb. 9 while iOS 8.2 was still being tested. While the 8.2 build, rolled out on March 9, is focused primarily on integration with the Apple Watch, the still-to-be released iOS 8.3 will introduce new features such as wireless CarPlay connectivity support, a new interface for an emoji picker, Google's 2-step verification support, and Apply Pay support for the China UnionPay network. The update will also give Siri, Apple's proprietary digital assistant, new languages, including Danish, Dutch, English (India); English (New Zealand), Portuguese (Brazil), Russian; Swedish, Thai, and Turkish. 

Most of the invites for the iOS 8.3 beta will come to those who have already participated in the OS X Yosemite public beta program.

According to the invite, "The iOS 8.3 Beta is available for download from the new Apple Beta Software Program website. Try it out and submit your feedback. You can use the iOS 8.3 Beta while continuing to use the OS X Yosemite 10.10.3 Beta. And with the all-new Photos app for Mac and iCloud Photo Library, you can now access your entire library on all your devices."