The game is played in an open world and from a first-person perspective. The player controls a character named Beatrix LeBeau, a rancher who moves to a planet far from Earth called the Far Far Range to live the life of a "slime rancher", which consists of constructing her ranch and exploring the world of the Far Far Range in order to collect, raise, feed, and breed slimes. Slimes are gelatinous living organisms of various sizes and characteristics. To progress she has notes left by the former owner of the ranch that help her on her journey through the Far Far Range.[7][8][9][10]
The game's main economic aspect revolves around feeding slimes the appropriate food items so that they produce "plorts", which can then be sold in exchange for Newbucks, which can be used to purchase upgrades to the rancher's equipment or farm buildings. With the exception of the basic pink slime, slimes will only eat one of the three types of food; fruit, veggie, or meat. Each slime also has a favorite food, which will lead the slime to produce twice the amount of plorts when eaten. The player moves the character around a variety of environments and is able to collect a variety of slimes, food items, and plorts by sucking them up with their vacuum tool (called a "Vacpack", a portmanteau of vacuum and backpack). They can only store a limited number of items and item types at a time and must unload their collected items before being able to collect more. The player must buy and upgrade various enclosures to house their collected slimes and farms for storing their food. Upgrades can also be aesthetic upgrades to the character's home, Vacpack, and the ranch itself. Two types of slimes can be combined and enlarged by feeding a slime a plort from another species, making them noticeably larger, combining their physical characteristics, and allowing them to produce two plorts when fed, one plort of each of their base slimes. They also share the favorite food of each of their base slimes. These hybrid slimes are known as "Largos".[11][12][13] However, if a Largo slime consumes a plort different from either species of slime it is made of, it becomes an aggressive malevolent black slime called the "Tarr", which converts attacked slimes around it to Tarrs, as well as being able to damage the player. The player can pump fresh water from ponds and springs to splash and disintegrate the Tarrs.There are different kinds of slimes in the game, each species differing in traits, ranging in complexity from simple ears, colors, wings, and tails, to the ability to teleport or grab items via a vine that emerges from the ground. Some of the types of slimes available in game include docile, harmful, non-farmable, and feral. Most slimes also have a "Gordo" version of themselves, which can be found in various hidden areas across the Far Far Range. These Gordos are extremely large and cannot move around like regular or Largo slimes. Players can shoot food items at them until they explode (50 of their food type, or 25 of their favorite food), leaving behind normal versions of the Gordo slime's species and crates containing random loot and either a teleporter or "slime key" which allow access to new areas or shortcuts between known areas.