GLSL Sandbox is described as 'An online GSGL Shader Gallery and live development tool. You can freely add to it without an account'. There are more than 10 alternatives to GLSL Sandbox, not only websites but also apps for a variety of platforms, including Windows, Linux, Self-Hosted solutions and iPhone. The best alternative is Shadertoy, which is free. Other great sites and apps similar to GLSL Sandbox are Shader Editor (Free, Open Source), SHADERed (Free, Open Source), Shade - Pro Shader Editor (Freemium) and GSN Composer (Free).
Create and edit GLSL shaders on your Android phone or tablet and use them as live wallpaper. A live-coding editor with syntax-highlighting lets you see results transparently in the background as you code and provides ample workspace to focus on your ideas.
SHADERed is a lightweight tool for creating and testing HLSL and GLSL shaders. It is easy to use, open source and frequently updated with new features. FEATURES - Configurable, dock-based interface. - Geometry as well as vertex and pixel shader support.
Shade transforms your device into a professional node-based shader editor. Build stunning, connected shader graphs that render in real time. You'll find full support for keyboard shortcuts, drag-and-drop, and documentation built right in.
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.
ShaderLab is the WebGL2 GLSL Editor for the browser. Code your shaders right in your browser with a live view to progress in the background. Then share and garner feedback through comments and check out other creators.
Shader Frog lets you create visual effects by composing two or more shaders together, and tweaking their parameters. You can build a complex effect out of simple components. You can then export your shader for use in your THREE.js game or application.