What is PS4 crossplay and what games use it?

Now that Sony says any PS4 game can use crossplay what titles are actually taking advantage of it and how does it work?

26 Cross-Platform (PS, Xbox, PC, Switch) Games to Try Today - Geekflare

Cross-platform play - Wikipedia

These are the best PC and PS4 crossplay games

Cross-Play: Games You Can Play With Friends Over PS4, Xbox One, Switch, And PC - GameSpot

Cross-Play: Games You Can Play With Friends Over PS4, Xbox One, Switch, And PC - GameSpot

All cross-platform games (PS5, Xbox Series X, Switch, PC, and more)

Can PS5 owners play with PS4 gamers? Everything you need to know about crossplay

Is Astroneer Crossplay or Cross Platform? [2023 Guide] - Player Counter

Cross-Play ➜ Battlefield 2042

Step-By-Step: How To Do Cross-Play With iOS, Xbox One, PS4 And PC In 'Fortnite Battle Royale

20 Best Cross Platform Games (Xbox, PS5, Switch, PC)

Crossplay Explained — The Texas Chain Saw Massacre

13 Best Crossplay Games for Consoles and PC (2023): Xbox, PlayStation, Switch, Mobile

Best crossplay games: play with friends across platforms

PlayStation 4 opens up cross-platform play, starting with Fortnite, PlayStation