Fortnite is playable across multiple platforms and it doesn’t have a high set of system requirements which means that those on older PCs can play it as well, although not necessarily at the most ideal settings. This is a big reason why it is popular.
If you are playing on an older PC and would like to see a boost in performance in terms of framerates, Epic has announced on their website that they will be introducing a Performance Mode on PC. It will help boost the performance of the game, especially on older or lower-end PCs.
Epic says, “Beginning December 15th, we’re launching a new performance mode on all PCs that meet Fortnite’s minimum specifications. Available in Alpha, Performance Mode will be selectable through the in-game settings menu and offers significant performance gains by trading out visual quality to lower memory usage and lighten the load on CPU and GPU. For players already on low scalability settings or less powerful hardware, this mode will allow the game to run better than ever before and maintain a smoother framerate.”
So this update seems to be more focused on gamers with older hardware who want smoother gameplay over better graphics. This is great for those with older PCs.
Source Ubergizmo