World switching, also known as world hopping, exploits a side effect of the duplicate worlds within the RuneScape game.
Each RuneScape world is hosted on its own computer, known as a server. Servers are continuously connected to the internet, and receive tie-ins from connections of players all over the world. The servers host these players (up to 2000 on a single server) while they play RuneScape. To ease strain on the servers running RuneScape, Jagex created many different servers as to not overload a single server with too many players. Unlike many other MMORPGs, a single character can visit any of the worlds.
Players log into that server and are able to interact with all of the elements — monsters, buildings, items, etc. — found on that world. These worlds, each located on its own server, are identical in form and yet independent of each other. Actions taken on World 1 will not affect the building, monsters, or items on World 2. For example, buying all of the chisels in the Lumbridge General Store on World 1 will not reduce the number of chisels in Lumbridge General Store on any other world. The side effect of these semi-duplicate worlds is if a store is overstocked or out of stock, or a mine is too busy or mined out for now, players can return to the world select screen and try a different world.
When a player stays in a particular location — such as a shop or ore spawn — while changing worlds, this is called world hopping.
An update on 21 May 2015 has allowed players to freely hop between worlds by clicking on the logout button (). Within the logout interface shows the world switcher button, where players can easily switch between worlds around Old School RuneScape. Players can also favourite up to two worlds at a time.
There are a few restrictions. Players cannot switch worlds if they have recently been in combat or have switched worlds multiple times in a row.
Players will be warned if they click on a PvP world (Worlds 325, 337, 392 and 417).
World switching can be very important in merchanting as prices often vary between worlds. This is noticeable in the Fishing shop in Port Sarim, particularly with the prices of lobster and swordfish. Another type of merchanting is called vial hopping. It consists of buying out the stock of Herblore potion vials in a particular shop then switching worlds and repeating the process.
World switching is also used to effectively mine runite ore, which, given the small number of rocks per world and a long respawn time, is very difficult to obtain at a decent rate without world switching.
The NPC named Hopleez pokes fun at world hopping as a whole (due to him being a parody of other players telling each other to hop worlds so that multiple players aren't fighting for the same resources).