FTEQW
FTEQW is an advanced and portable Quake engine. It supports multiple games running on idTech, plus its own set of games that developers have created.
 
Hot Soup Processor
Hot Soup Processor is an interpreter used for developing 2d and 3d games, starting development since NEC PC88 times
 
Narrat Engine
Narrat is a beginner-friendly game engine for making narrative games with RPG features, visual novels, interactive fiction, and more
  Luna Visual Novel Engine
Luna is a visual novel engine made using JavaScript.
 
KorGE Engine
Modern Multiplatform Game Engine for Kotlin
  KAPLAY
KAPLAY is a JavaScript and TypeScript game library that makes it easy to create games for the web. It's free, open-source and fun.
  8th Wall
The 8th Wall Studio Game Engine is a powerful, browser-based development environment designed to build cross-platform 3D & spatial (XR) games directly on the web.
  anitya
anitya is offers a low-code software toolkit designed to empower creators brands to effortlessly develop immersive 3D experiences, including gamified training modules, collaborative workshops, and e-commerce solutions.
 
modd.io
Modd.io is a low-code game engine where you can play & make games all in a browser with built-in netcode and free server hosting
 
FlatRedBall
A game development platform built in C#
 
Hology Engine
A versatile game engine designed for creating 3D games and experiences. It includes landscape sculpting, a physics engine, customizable shaders, and procedural foliage generation.
  Flowlab
A no-code game maker that runs right in your browser. Flowlab makes it easy to get started making your own games. Publish your creations as iOS or Android mobile apps, or export for PC & Mac.
  Sundown
An extendible WebGPU game and simulation engine for fun, games and research.
 
GameSalad
A game engine to build 2D games with no code.
  Love2D
A free and open-source framework to make 2D games in Lua
 
Polygonjs
A procedural, node-based design & animation tool, for the web
 
DragonRuby 2D Engine
DragonRuby Game Toolkit is a professional grade cross-platform 2D game engine
  Three.js
An easy to use, lightweight, cross-browser, general purpose 3D library
 
Construct 3
Construct 3 is a powerful and user-friendly game development engine without the need for extensive coding knowledge
  MEG-4
Very performant fantasy console with lots of features and multiple languages
  Oxygengine
Oxygengine is an all-batteries-included kind of engine, focused on being Web-first but slowly moving more into more platforms such as desktops and consoles
  App Game Kit Studio
Vulkan powered cross-platform coding
 
microStudio
microStudio is a free, open source game engine online
 
HaxeFlixel
A cross-platform game engine built with Haxe
 
Heaps.io
A mature cross platform graphics engine designed for high performance games. It was used in major titles like Dead Cells, Dune Spice Wars, Northgard and Wartales.
 
WASM-4
WASM-4 is a low-level fantasy game console for building small games with WebAssembly
  A-Frame
A web framework for building virtual reality experiences
 
Urho3D
Urho3D is a free lightweight, cross-platform 2D and 3D game engine
 
Calico
An interactive fiction engine for web games, powered by Inkle's ink
  Retro Puzzle Maker
A tool to help you create new puzzle games you can play on an NES