If you want an experience like Claude's "Artifacts" or a built-in sandbox for HTML/JS previewing, these are the top open-source contenders.
Extremely polished UI. It supports a plugin system and features a Code Preview mode that renders HTML/CSS/JS directly in the chat window.
Developed by LangChain. It is explicitly built to mimic the Claude Artifacts experience, focusing on side-by-side editing and rendering of code/documents.
This is the ultimate tool for full-stack HTML/React rendering. It runs a full WebContainer in your browser to build and preview apps live.
A powerful alternative to ChatGPT. While general-purpose, it has a robust Code Interpreter and plugin system for rendering visualizations and HTML.
A desktop/web client that offers very clean code block management and simple web preview capabilities for quick HTML snippets.
Don't switch yet! Open WebUI supports "Functions" and "Tools" where you can install community "Artifacts" filters that enable HTML rendering.