Javascript decorators are currently a stage 3 proposal, meaning they will soon be implemented in Javascript engines. But decorators can already be used today (with Babel or Typescript), and many of you are probably already familiar with them from frameworks such as Angular or MobX. They enable library authors to build new kinds of APIs, and in this talk, we're gonna do a deep dive into the current proposal, how you can use them in your libraries, and what to look out for. There will be lots of examples that you will be able to apply directly after the talk.