Apps similar to ShaderPad include The Book of Shaders, which is free. Other options are ShaderWorkshop and OpenGL Shader Designer. In total there are three Code Editors like ShaderPad for Windows, Linux, the web and self-hosting.
The Book of Shaders provides a gentle, step-by-step guide through the abstract and complex universe of Fragment Shaders. Besides scores of insightful illustrations, the site includes a very intuitive live-coding editor for users to easily see changes as they code.
Shader Workship is an interactive GLSL fragment shader editor inspired by ShaderToy and built with Qt.
TyphoonLabs' OpenGL Shader Designer is an open-source shader development IDE created for writing vertex and fragment shaders in the OpenGL Shading Language (GLSL).
