It is hoping new augmented and virtual reality web developers will pick its new cloud-based platform over Unity3D and Unreal Engine.
The blog post boasts that you can make apps "with ease" and "don’t need any 3D graphics or specialized programming knowledge to get started".
There's a hefty dose of big players suddenly up and offering their own AR and VR development apps, including Apple, Google and even Microsoft.
In an FAQ, Amazon said Sumerian does "share similarities in feature sets" with its existing downloadable video game engine, Lumberyard, but Sumerian is web-only.
There is also apparently ARKit support, but no ARCore or Unity Projects yet (just a vague promise of "coming soon").
You can edit scenes in Firefox Quantum 57 and Chrome 62 freely, or chance "a slightly degraded experience" in Edge or Safari browsers.