Screenwriting tools tend to be on the pricey side when it comes to software, but Amazon's released a free tool called Storywriter that provides a barebones screenwriting tool that saves directly to the cloud.
Amazon Storywriter automatically formats for dialogue, transitions, and action descriptions. The only font choice is Courier, and it will export to PDF, FDX, or Fountain. The app also comes with a Chrome extension that allows you to work offline. You can also submit your script directly to Amazon Studios from the app, if that's your thing, but be aware that there's a pretty big "similar content" agreement clause that details exactly what Amazon can take from your script without giving you any credit. The app itself is pretty run of the mill when it comes to screenwriting tools, but the free price tag is an appealing option for anyone looking to get started writing screenplays.