Get it while you can and play through it before the sequel arrives.
Last month, Sony decided to make Abzû, Astro Bot Rescue Mission, Enter the Gungeon, Moss, Paper Beast, Ratchet & Clank, Rez Infinite, Subnautica, The Witness and Thumper free for everyone with a PlayStation 4 or PlayStation 5. That wasn't all, however, as we were also told Guerrilla's latest gem would join the fun on April 20. That's today, folks!
Yes. You can now add Horizon: Zero Dawn - Complete Edition to your library completely free, and it's yours to keep forever as long as you do so before May 15. This version includes the The Frozen Wilds expansion and a few other goodies, so you're completely set to dive into Horizon Forbidden West after playing through it. Just click here to add it now.
It's also worth noting that eight of the games mentioned in the first paragraph can only be added to your collection for free until 4 AM BST / 5 AM CEST on April 23, which means you only have three days left if you haven't done so already. Those games can be found here.