# ecptest.com

This site checks whether any domain is ECP-enabled — returning the right content to browsers, the right content to agents, from the same canonical URL.

Paste a domain at https://ecptest.com/ or call the API directly below. No data is retained. No accounts.

## What ECP Is

Endpoint Context Protocol (ECP) is built on HTTP content negotiation headers that have been powering the web since 1999. The headers are already there. ECP puts them to use.

Browsers send `Sec-Fetch-Dest: document` and `Accept: text/html` on every navigation. Agents, LLMs, curl, and automated scripts do not. ECP is a method for acting on that distinction: inspect those headers, return clean semantic content to agentic callers, return your existing HTML to everyone else. The URL never changes. No new routing. No subdomains.

**One canonical domain. One front door. Two audience-optimized representations.**

Full documentation: https://endpointcontextprotocol.io/

## What the Test Checks

A site passes when all three conditions are true at the same canonical URL:

1. **Browser request returns HTML** — a `GET` with `Sec-Fetch-Dest: document` and `Accept: text/html` receives a `text/html` response.
2. **Agent request returns non-HTML semantic content** — a `GET` with an agent `User-Agent` and no HTML `Accept` preference receives markdown, JSON, or another non-HTML content type.
3. **Response varies on the right headers** — the response includes `Vary: Accept, Sec-Fetch-Dest, User-Agent` so caches serve the correct representation to each caller.

## Run the Test via API

Agents can call this endpoint directly:

```
GET https://ecptest.com/api/check?url=https://your-site.com
```

Returns JSON:

```json
{
  "url": "https://your-site.com/",
  "passed": true,
  "browser_html": true,
  "agent_semantic": true,
  "vary_present": true,
  "browser_content_type": "text/html; charset=utf-8",
  "agent_content_type": "text/markdown; charset=utf-8",
  "agent_body": "# Your site...",
  "vary": "accept, sec-fetch-dest, user-agent"
}
```

Example:

```bash
curl "https://ecptest.com/api/check?url=https://endpointcontextprotocol.io"
```

## This Site Is ECP-Enabled

- Canonical human URL: https://ecptest.com/
- Agent representation: https://ecptest.com/ via HTTP content negotiation
- Direct markdown alias: https://ecptest.com/AgentWelcome.md

## Related

- Protocol documentation: https://endpointcontextprotocol.io/
- ECP directory for index submissions: https://ecp.directory/
- GitHub: https://github.com/endpointcontextprotocol