Pixel Crosshair turns the plain dot in the middle of your screen into something you drew yourself.
Press H in any world and a 32×32 canvas opens over the game. Paint with the left click, erase with the right click, and pick a color from the row underneath. Save a design, click one of your four latest crosshairs, then hit Apply. The next time you look down a cave or line up a shot, that crosshair is the one in the center.
It is client-side only, so it works on single-player and servers without anyone else installing it. The key can be changed in Controls, and your drawings stay saved after you quit. One jar runs on Fabric, Forge, and NeoForge for Minecraft 26.2.

