Included in Preview 1 are improvements to the proxy LOD tool, as highlighted in the May 17th livestream, many mobile improvements and optimizations we've made for Fortnite on iOS and Android, and beta to mixed reality capture. Niagara will be rolling out in beta, and you’ll also see a number of our GDC features, including the new cinematic depth of field and improved rendering features for digital humans at your disposal.
To get Unreal Engine 4.20 Preview 1, head to the Library section on the launcher, select “Add Versions” and choose 4.20 Preview 1.
A more inclusive list of upcoming changes in the build has been posted on our forums, where you can leave feedback. Please keep in mind that Preview releases are intended only to provide a sample of what is going to be released in the update and are not production-ready.
We recommend waiting for the full release of 4.20 before updating your projects to the new engine version. For now, please use copies of your projects to test new features.