Different VRR formats
Unfortunately, there isn’t just one format of Variable Refresh Rate. VRR began life in the PC gaming domain, where two graphics card manufacturers - AMD and Nvidia - are locked in an eternal battle for supremacy, and each one has its own VRR format: AMD’s is called FreeSync and Nvidia’s is G-Sync.
If you’re a PC user, the VRR format you can use will depend on which of the two companies manufactured your graphics card.
It's widely believed that a TV needs to support either Freesync or G-Sync in order to support VRR from game consoles, but this isn't actually the case. That's because there's a little talked about third VRR format, called HDMI Forum VRR, or even just HDMI VRR.
This VRR format is part of the
HDMI 2.1 spec and is starting to appear on a fair few TVs, even some that officially have only HDMI 2.0 sockets. It's also worth noting that a TV that supports HDMI 2.1 won't definitely support HDMI VRR, although it is likely.