Just adds a keybind (default "C") which sets the player to the crawling pose, allowing them to sneak through 1-block high gaps, without needing to squash something on top of them.

Also adds a second keybind (not bound to anything by default) which allows you to toggle being prone.

Has server side config options to allow/deny players going prone in certain scenarios (can be found in <world save>/serverconfig/goprone-server.toml).

Config defaults to:

Allow jumping while prone
Allow during flight (player not on ground).
Deny while riding another entity (horse, pig, minecart, boat etc.).

From v2.0.0 the exceptions are handled by adding entities to the #goprone:blacklisted_entities or #goprone:whitelisted_entities (depending on whether or not it is enabled for entities in the config file.
Between v1.2 and v1.7 the exceptions were handled with an exceptions list inside the config file. Any entities listed by their registry name (e.g. "minecraft:boat") will invert the general rule.

Requires Forge. (Fabric version here, Maintained by VidTu with my permission)

Needs to be installed on the server (although if it isn't you can still join the server, the mod just won't do anything)!

Not required on the client (Although clients without it will not be able to go prone as they won't have the keybind).

You may use this mod in modpacks and/or videos without asking permission.

Thanks to hairyballbastic for the new logo.