UE5 WebUI: Add widget to viewport, set URL to file:///…/ui.html. Enable CEF in Project Settings.
Unity WebGL: Place HTML in Assets/WebGLTemplates/. Use jslib bridge for game→UI events.
GDevelop: Use the External HTML layer extension, point to exported file.
Web/Vercel: Drop the HTML file into your project root and link from your game's HUD layer.
AI Handoff
Exports include a machine-readable <!-- HYDRA AI HANDOFF --> block with full component schema, layout intent, and re-import JSON so any LLM can understand and modify the UI without the editor.