AFTER OFFICIALLY REVEALING its update at its Build developer conference two weeks ago, Microsoft has released its Windows Phone 8.1 preview to developers today.

The update, which includes the introduction of Microsoft’s long-awaited personal voice assistant Cortana (which is only available in the US for now), an action centre and an improved navigation and keyboard service, won’t be made available to regular users until the summer when the first phones supporting it arrive.

Registered Windows Phone developers can download the update now, but for those who aren’t but still want the update, they can sign up through the Windows Phone App Studio site and set up a project.

Once that’s done, you can then download the preview app which detects the update for you.

Since this version of Windows Phone 8.1 is an early version, certain features like the custom lock screen support aren’t available yet and there will be some bugs too as Microsoft prepare it for its official release.

If you do decide to update, you won’t be able to return to the previous version, Windows Phone 8.

The majority of features that was announced for the update are available in this developer preview, but only US users will have access to Cortana.

Microsoft says the digital assistant will be made available to the UK and China during the second half of the year, with other countries to follow afterwards in 2015.

Read: Microsoft brings Siri rival Cortana and an updated look to Windows Phone >

Read: Microsoft says goodbye to XP by releasing Windows 8.1 update >