This mod requires Fabric, not Forge.
Dynamic FPS automatically reduces the speed at which minecraft renders when it's not focused (to 1 FPS) or hidden (no renders at all). It also fixes a bug in Vanilla Minecraft that makes it take much more performance in the background than it should, as well as making the game not render while reloading resources (which makes it take forever on my machine!).
Is this just like the FPS Reducer mod? If so, what are the benefits?
In reply to Swordee77:
I guess the only real difference is that this one uses Fabric.
As Shyning pointed out, this mod uses Fabric rather than Forge, so if you want to play with Fabric mods, you won't be able to combine them with FpsReducer (at least not yet), so this offers a nice alternative. Additionally, FpsReducer actually configures the FPS Minecraft is set to, while this mod simply makes it render less (or not at all if it's hidden, which FpsReducer doesn't distinguish), which has the benefit of it "coming back to life" instantly once you switch back to the game. FpsReducer, on the other hand, takes a couple frames (which can take a while, depending on how strongly you set it to reduce your FPS) to get back to normal.
In reply to Juliand665:
My bad! I had thought FPSReducer was a fabric mod as well, thanks for your explanation.