A custom RSPS adds content you won't find in RuneScape itself: new items, bosses, areas, skills or whole systems such as perk trees and upgrades. Some are "semi-custom", mostly OSRS with custom extras on top. Others are built almost entirely from scratch and barely resemble the original game.
Players who've done what RuneScape has to offer and want something new to learn. Players who enjoy working out new builds and gear setups, and those who like a game that changes with every update.
How much is custom and how much is the original game. Whether the custom content is finished or still "coming soon". How balanced it feels: custom items have no official numbers to copy, so quality varies a lot. How often the server updates, and what its store sells.
Servers whose main category is Custom come first. Below them are other servers tagged Custom. Both parts are ranked by votes cast this month: anyone can vote once every 12 hours, free and without an account, and the ranking starts over on the 1st. Votes can't be bought, and ads never move a server up.
What does "semi-custom" mean? A server that keeps the original game as its base, usually OSRS, and adds a layer of its own content on top.
Is a custom server still based on OSRS? Often, at least partly. Check the version tag on the listing: OSRS, pre-EoC or RS3.
Are custom servers pay-to-win? Some are, many aren't. Look at what the store sells before you invest your time.
A pre-EoC RuneScape private server with custom raids, custom world bosses, and multiple Ironman modes.
OSRS
Download only
Custom
AsteriaPS
PRE-EOC
Ironman Modes
RS3
Gambling
PvP
PvM