S&box

In September 2015, Garry Newman, the creator of Garry's Mod, first mentioned that a sequel was in development. In September 2017, Facepunch Studios officially unveiled S&box as a prototype. This early version was built using Unreal Engine 4 (UE4), incorporating a hotloading C# layer. The developers used UE4 for core features like rendering, networking, and physics. At this point, it was uncertain whether S&box would be released as a moddable platform or used internally by Facepunch.

In March 2020, it was suggested that S&box was the sequel to Garry's Mod. However, the project was put on hold while the team decided to switch engines. The team eventually chose Source 2 by February 2021, the same engine used to create Half-Life: Alyx. This decision was made to make it easier to transfer tools from Garry's Mod and to update the engine with tools like ModelDoc and AnimGraph.

User reviews posted online to Steam for S&box shortly after its release were reported to have been "mixed" by gaming sources. In a Steam Deck HQ article released on the game's launch day, Noah Kupetsky wrote that "[he] can see it getting better and better as the community starts to build it," but would also surmise that "[it's] not the greatest experience, but it's definitely okay." Writing for PC Gamer, Morgan Park would challenge the developers' claim that S&box was the "'spiritual successor' to Garry's Mod", arguing that the introduction of microtransactions and quality of content on release were too disqualifying, saying "if that spirit is present, I've yet to encounter it. None of the qualities that made Gmod an amazing, lasting anomaly of PC gaming are relevant to what Facepunch has actually made here: Roblox."

S&box has received criticism for containing AI slop, with IGN reporting on the backlash amongst users unhappy over it hosting games created through the use of generative AI in April 2026. In a response, Newman stated that "[we] don't encourage using AI to be creative. We don't encourage using AI to create games for you. We'll be taking action to promote human creativity and push obviously AI-created slop off the main page."