Unity is a cross-platform game engine developed by Unity Technologies, first announced and released in June 2005 at Apple Worldwide Developers Conference as a Mac OS X game engine. The engine has since been gradually extended to support a variety of desktop, mobile, console and virtual reality platforms. It is particularly popular for iOS and Android mobile game development, is considered easy to use for beginner developers, and is popular for indie game development. Wikipedia

Godot is a cross-platform, free and open-source game engine released under the permissive MIT license. It was initially developed by Argentine software developers Juan Linietsky and Ariel Manzur for several companies in Latin America prior to its public release in 2014. The development environment runs on many platforms, and can export to several more. It is designed to create both 2D and 3D games targeting PC, mobile, and web platforms and can also be used to develop non-game software, including editors. Wikipedia

Unreal Engine (UE) is a series of 3D computer graphics game engines developed by Epic Games, first showcased in the 1998 first-person shooter video game Unreal. Initially developed for PC first-person shooters, it has since been used in a variety of genres of games and has been adopted by other industries, most notably the film and television industry. Unreal Engine is written in C++ and features a high degree of portability, supporting a wide range of desktop, mobile, console, and virtual reality platforms. Wikipedia

GDevelop is a 2D and 3D cross-platform, free and open-source game engine, which mainly focuses on creating PC and mobile games, as well as HTML5 games playable in the browser. Created by Florian Rival, a software engineer at Google, GDevelop is mainly aimed at non-programmers and game developers of all skillsets, employing event based visual programming similar to engines like Construct, Stencyl, and Tynker. As it was distributed under an open-source license, GDevelop has found used in games education, ranging from primary schools to university courses. It has also been used by educators and researchers to create learning and serious games. Wikipedia

Torque Game Engine, or TGE, is an open-source cross-platform 3D computer game engine, developed by GarageGames and actively maintained under the current versions Torque 3D as well as Torque 2D. It was originally developed by Dynamix for the 2001 first-person shooter Tribes 2. In September 2012, GarageGames released Torque 3D as open-source software under the MIT License. Torque 3D features a world editor suite including tools for sculpting terrain and painting forests, drawing rivers and roads, as well as material, particle and decal editing. It supports the open COLLADA file format as interface to 3D digital content creation software. PhysX provides support for cloth dynamics, rigid body dynamics, destructible objects and joints, as well as fluid buoyancy simulation. Other features include a deferred lighting model and modern shader features such as dynamic lighting, normal and parallax occlusion mapping, screen space ambient occlusion, depth of field, volumetric light beam effects, lens flare/corona effects, refraction, bloom, blurring and color correction, among others. Networking functionality for multiplayer support is included as well. Build support is provided for desktop Windows, Linux, macOS and Web platforms Wikipedia

PlayCanvas is an open-source 3D game engine/interactive 3D application engine alongside a proprietary cloud-hosted creation platform that allows for simultaneous editing from multiple computers via a browser-based interface. It runs in modern browsers that support WebGL, including Mozilla Firefox and Google Chrome. The engine is capable of rigid-body physics simulation, handling three-dimensional audio and 3D animations. PlayCanvas has gained the support of ARM, Activision and Mozilla. The PlayCanvas engine was open-sourced on June 4, 2014. In April 2019, BusinessInsider.com reported that the company was acquired by Snap Inc. in 2017. Wikipedia

MonoGame is a free and open source C# framework used by game developers to make games for multiple platforms and other systems. It is also used to make Windows and Windows Phone games run on other systems. It supports iOS, Android, macOS, tvOS, Linux, PlayStation 4, PlayStation 5, PlayStation Vita, Xbox One and Nintendo Switch. It implements the Microsoft XNA 4 application programming interface (API). It has been used for several games, including Bastion, Celeste, Fez and Stardew Valley. Wikipedia

Stencyl is a video game development tool that allows users to create 2D video games for computers, mobile devices, and the web. The software is available for free, with select publishing options available for purchase. The software was originally called "StencylWorks" while in development and for the initial release but was later shortened to just "Stencyl". Wikipedia

Defold is a cross-platform, free, and source-available game engine developed by King, and later the Defold Foundation. It is used to create mostly two-dimensional (2D) games, but is fully capable of three-dimensional (3D) as well. Defold is a downloadable desktop app, and ships with its own embedded IDE. Defold targets desktop, mobile, web, and console platforms. The development model of the maintainers (Source-available) keeps the engine free to use, because it is maintained by its community. Defold has over 30,000 users, and has been used to publish over 100 games. Exported games with Defold typically use less than 100kB RAM and very small bundle sizes, less than 2 MB, due to the Engine's modularization and efficient core. Wikipedia

Stride (formerly Xenko and Paradox) is a free and open-source 2D and 3D cross-platform game engine originally developed by Silicon Studio. It can be used to create video games for PC, mobile devices and virtual reality. Stride, then called Xenko, was originally made available by Silicon Studio under a dual-license model, available to anyone under GNU GPLv3, with alternative, for-pay license terms available for those for whom the GPL's copyleft terms are a barrier to adoption. On August 2, 2018, developer Virgile Bello announced on the Xenko blog that Silicon Studio had dropped support of the project and relicensed Xenko 3.0 under the MIT License. Unlike the prior dual-license arrangement whereby the engine was available as free and open-source software but the editor remained proprietary, under the new arrangement both the engine and the editor are available under the MIT License. Wikipedia