reactor.gitbook.io or the Steakunderwater forums. Stay away from any site asking for payment—Reactor is open source, and that’s its superpower.
Here’s a clear, informative piece on downloading and installing the for DaVinci Resolve. Unlock DaVinci Resolve’s Hidden Power: How to Download & Install Reactor If you use DaVinci Resolve (especially the free version) and feel limited by its native tools, Reactor is a game-changer. Reactor isn’t a single effect but a package manager —an open-source hub that lets you instantly install hundreds of macros, scripts, fuses, and transitions with one click.