Dynamic FPS can reduce the frame rate, volume, and pause toasts while Minecraft is not focused or hidden.
In addition to this it also fixes a bug in vanilla Minecraft making it take too many resources in the background.

Download on GitHub Releases, Modrinth, or CurseForge.

Dynamic FPS will detect when the window is not focused, but instead either hovered over, unfocused, or invisible.
For each mode you can adjust the maximum FPS, master volume, toast visibility, and whether to invoke garbage collection.

In addition to this Dynamic FPS also reduces background CPU usage and stops rendering the world while either the loading overlay is active or a screen is obscuring the world (e.g. when you're editing keybinds or in another screen that the mod detects as opaque).

• Why is Minecraft still running at 15 FPS?

Dynamic FPS will only reduce the client / render loop to a minimum of 15 cycles per second. Lower frame rates are achieved by then cancelling the rendering of all superfluous frames, eg. 14 out of 15 frames are cancelled for 1 FPS.

This lets you resume playing almost instantly after switching back to the game: Instead of having to wait for up to a second until the next rendered frame comes along, the game checks back within 1/15th of a second.

If Dynamic FPS' optimizations conflict with a feature of your mod you can disable them.
This is done by adding a dynamic_fps object to your mod's metadata (inside quilt/fabric.mod.json).

Force disable the loading overlay optimization:

    "dynamic_fps": {
        "optimized_overlay": false
    },

Screen optimization is enabled for screens that call renderDirtBackground/renderBackgroundTexture.
Other screens can opt in or out by adding their package and class name to the optimized_screens object instead:

    "dynamic_fps": {
        "optimized_screens": {
            "enabled": [
                "com.example.example_mod.gui.screens.ExampleScreen"
            ],
            "disabled": []
        }
    },