Full-screen, DirectX 11 applications that do not natively support variable refresh rates (VRR) might suddenly start working with GSync and Adaptive-Sync. A Microsoft Developer Blog post discusses the new feature for Windows 10 Version 1903. It is off by default, because blindly upending what a video game assumes is bad, but it can be enabled in the Windows 10 graphics settings screen.

This feature requires the following three conditions:

  1. Windows 10 is at version 1903 (or later)
  2. You have a G-SYNC or Adaptive-Sync monitor attached to the system AND
  3. Your GPU has up to date, WDDM 2.6 drivers

The slider will not be present on machines that do not satisfy all three conditions.

Also, this toggle does not affect games that natively support G-SYNC or Adaptive-Sync. This only affects games that would be incompatible without it. Other games, which support VRR directly, will be managed by your GPU driver control panel (etc.) as always.