The GSN Composer is a free online tool for node-based visual programming. It is especially intended for educational purposes, such as computer graphics courses and tutorials.

The built-in shader editor allows rapid prototyping of GLSL shaders. Importantly, the created GLSL code is generic and can be used directly in other OpenGL/GLSL applications. Custom data for the shader’s UNIFORM and IN variables can be easily supplied via the visual interface, which is the main advantage compared to other web-based shader editors.

The shader editor was now upgraded to WebGL2 and supports GLSL ES 3.0 code. WebGL2 allows shaders with multiple render targets (MRT). For each additional OUT variable in the shader code, the interface automatically creates a corresponding output image. This facilitates G-buffers and deferred shading. Furthermore, examples for physical-based rendering (PBR) and HDR environment lighting are provided.