Best Cross-Platform Game Servers for self-hosting

Tower-defense and factory game with servers

Replaces Factorio

Open-source remake of RollerCoaster Tycoon 2

Replaces RollerCoaster Tycoon

Open-source turn-based survival roguelike

Replaces NetHack

Open-source reimplementation of Civilization V

Replaces Civilization V

Open-source Minecraft launcher for managing instances and modpacks

Replaces Official Minecraft Launcher, CurseForge app

OpenTTD

Game Servers

Open-source transport simulation game with servers

Replaces Transport Tycoon

Minimalist text adventure game for your browser

Free space exploration and trading game

Replaces Escape Velocity

JavaScript library for creating Minecraft bots and automation

Replaces commercial game bot frameworks

Turn-based fantasy strategy with multiplayer server

Replaces Heroes of Might and Magic

Visual novel engine for creating story-based games

Replaces TyranoBuilder

Open-source engine for Heroes of Might and Magic III with multiplayer

Replaces Heroes of Might and Magic III original

Bridge that lets Bedrock players join Java Minecraft servers

Replaces Minecraft cross-play workarounds

Free 3D kart racing game with online servers

Replaces Mario Kart

Narrative scripting language for interactive fiction games

Replaces Yarn Spinner

LinuxGSM

Game Servers

Command-line tool for dedicated game servers

Replaces TCAdmin, Multicraft

Unique puzzle game designed for geeks and developers, where you solve

Open-source 3D real-time strategy game

Replaces Command & Conquer

Open-source voxel world game and engine

Replaces Minecraft

Open-world multiplayer voxel RPG with servers

Replaces Cube World, Minecraft

Open-source engine for the S.T.A.L.K.E.R. games

Replaces original X-Ray Engine

Classic-style 2D side-scrolling platform game

Replaces Super Mario Bros

Open-source real-time strategy and economy game

Replaces The Settlers

Open-source tool for telling interactive nonlinear stories

Replaces Inklewriter

Maintained Quake III Arena engine with dedicated server

Replaces Quake III Arena original

Retro 2D multiplayer shooter with servers

Replaces Worms, Soldat

Browser-based open-source empire strategy game

Replaces Civilization

Free city-building simulation game

Replaces SimCity

Open-source reimplementation of Chris Sawyer's Locomotion

Replaces Chris Sawyer's Locomotion original

Open-source space adventure and trading simulator

Replaces Elite, Frontier

Add network play functionality to Rockstar North's Grand Theft Auto

Natural-language design system for interactive fiction

Replaces TADS

Free turn-based strategy game with a dedicated multiplayer server

Replaces Civilization

Open-source 2D real-time strategy and economy simulation

Replaces Anno series

Self-hostable open-source educational programming game

Replaces Commercial programming games

Open-source voxel FPS compatible with Ace of Spades servers

Replaces Ace of Spades

Open-source interpreter for RPG Maker 2000 and 2003 games

Replaces RPG Maker RTP runtime

Free FPS/RTS hybrid game with a self-hostable dedicated server

Replaces Tremulous

Free pixel-art real-time strategy game on the OpenRA engine

Replaces Command & Conquer

Lightweight multiplayer first-person shooter

Replaces Counter-Strike

Open-source turn-based space empire strategy game

Replaces Master of Orion

Minecraft protocol and bot library written in Go

Replaces commercial game bot frameworks

Implementation of Terraforming Mars board game

Open-source 2D space trading and combat game

Replaces Escape Velocity

Multiplayer server for The Elder Scrolls III via OpenMW

Replaces Morrowind single-player

Free open-source RTS with self-hostable multiplayer

Replaces Supreme Commander

Engine and editor for creating point-and-click adventure games

Replaces Visionaire Studio

Cooperative platformer based on Teeworlds

Replaces Teeworlds

Self-hostable chess server playing multiple chess variants

Replaces Chess.com

Open-source flight simulator with multiplayer

Replaces Microsoft Flight Simulator, X-Plane

Community patchpack extending OpenTTD multiplayer servers

Replaces Transport Tycoon

Maintained engine and server for Wolfenstein: Enemy Territory

Replaces Wolfenstein: Enemy Territory original

Open-source turn-based colonization strategy game

Replaces Sid Meier's Colonization

Fast-paced free arena first-person shooter

Replaces Quake, Unreal Tournament

Sandbox voxel game with multiplayer servers

Replaces Minecraft

Geography multiplayer game

CLI for executing queries on a remote Valve Source dedicated server

Open-source space trading and combat game inspired by Elite

Replaces Elite

Open-source city building and management game

Replaces SimCity

Turn-based artillery strategy game with servers

Replaces Worms

Fast-paced open-source arena first-person shooter

Replaces Quake, Unreal Tournament

An open-source 2D battle royale game inspired by surviv.io

Open-source dungeon-keeper-style real-time strategy game

Replaces Dungeon Keeper

Cross-platform Minecraft server manager

Open-source 3D real-time strategy game

Replaces Age of Empires, Warcraft III

Open-source multiplayer action and tactics game

Replaces Clonk

Open-source Yu-Gi-Oh card game client with self-hostable servers

Replaces Yu-Gi-Oh Master Duel

Admin, ban, and communication management system for games running

Fast-paced real-time strategy game for the Linux terminal

Replaces commercial RTS games

Virtual surface in the browser on which you can play board, dice

Replaces playingcards.io

Open-source voxel sandbox game for Luanti

Replaces Minecraft

Free Quake III-style arena shooter with servers

Replaces Quake III Arena

3D Tron-style lightcycle multiplayer game

Replaces Tron

Easy-Wi is a Web-interface that allows you to manage server daemons

Open-source strategy game of defending Earth from aliens

Replaces XCOM

Free Lemmings-inspired puzzle game with network multiplayer

Replaces Lemmings

Open-source transport and economy simulation game

Replaces Transport Tycoon

Survival voxel game playable on self-hosted Minetest servers

Replaces Minecraft

Dedicated server engine for the Nexuiz arena shooter

Replaces Quake III Arena

Survival sandbox game for self-hosted Luanti/Minetest servers

Replaces Minecraft

Geography game

Open-source 2D MMORPG with self-hosted servers

Replaces Ragnarok Online

Sync games and save files across multiple devices

2048 game clone

Set of games Framagames from Framasoft

Wordle-based online word game

Scrabble® game free play not enforcing rules

Create a virtual game room around a connected buzzer (documentation