FallPredict

A small HUD readout predicts the fall damage that would apply to the player if they stepped off the ground directly below their feet. Each client tick a downward ray is cast from the feet, and it stops at the first solid block or fluid surface it meets. The drop height from that point is converted to the damage vanilla would deal, using the real formula with ceil applied to the fall distance, so the number matches what the game would take away.

The readout is color-coded. Yellow marks a drop that is survivable but leaves about half health, orange marks a drop that costs more than half of current health, and red marks a LETHAL fall that would kill the player at their current health. Over a bottomless drop the readout reads Fall, and the badge only appears when there is an actual drop below, staying out of the way on flat ground beyond the vanilla 3-block safe height. A fall into water shows a low number, since the ray stops at the water surface.

The J key toggles the readout on or off, and an action-bar message confirms the new state. The code is under the MIT License and is not open source, and the mod runs on the client alone, so only the player who uses it needs the file, and Fabric API must be present.