After starting its developer-focused beta in May, Google have now moved the testing period for Android O into its final phase ahead of launch.

“As we put the finishing touches on the Android O platform, today we’re rolling out Developer Preview 4 to help you make sure your apps are ready,” Google said in a blog post.

“This is the final preview before we launch the official Android O platform to consumers later this summer. Take this opportunity to wrap up your testing and publish your updates soon, to give users a smooth transition”.

Android O will add a new picture-in-picture mode and new notification dots to the OS, as well as a number of under-the-hood improvements that will see devices boot faster, load apps quicker and operate in a way that’s more secure than previous releases.

It’s also understood that the update will bring important improvements to Bluetooth audio playback.

Previous reports have said that this year’s major update to the Android mobile operating system will come to Google Pixel first, with the managing editor of Android Police claiming it will do so within the first two weeks of August.