## What is "JavaScript-rendered"?
A page is JavaScript-rendered when the HTML the server sends is essentially empty — the actual content (headings, prose, product information) only appears after the browser downloads and runs a JavaScript bundle that mounts a framework like React, Vue, Svelte, or Angular into an empty root element.
A typical JS-rendered homepage looks like this on the wire:
```html
```
The visible `` content is zero bytes. Everything you see in a browser was constructed client-side after the JS ran.
## Why this matters for agents
Most AI crawlers do not execute JavaScript. When ChatGPT, Claude, Perplexity, Gemini fetches, or a typical agent framework hits your URL, they get the raw HTML — and your homepage is blank. Your product description, headings, links, and prose are invisible to them.
This is a real harm for retrieval and summarization. An LLM asked "what does this company do?" while citing your URL will produce a poor answer or hallucinate, because there is nothing on the page to read.
## What this does *not* break
Tags emitted into the static `` of your HTML are unaffected by client-side rendering. Even a fully JS-rendered SPA can pass these checks if the build tool populates the head correctly:
- JSON-LD structured data (`