# heade.rs

> Free web tool at heade.rs, made by Colin Armstrong, that looks up any domain, IP address or network (AS number) and reports its hosting, routes, latency, registration, DNS, email security, HTTP headers and support for AI crawlers and agents.

Every lookup has its own URL, `https://heade.rs/<domain | IP | AS number>`, such as https://heade.rs/github.com, https://heade.rs/1.1.1.1 or https://heade.rs/AS13335. Pasted URLs work too.

A domain or IP address report covers:

- Hosting: the address, its network (AS number), BGP prefix and RPKI status, location, and the cloud region, CDN, crawler, relay or Tor exit it belongs to
- Registration: the domain's registrar, dates and status, or the regional registry's record for an address
- DNS: its records, and whether they're signed with DNSSEC
- Email security: the mail provider, SPF, DMARC, MTA-STS, TLS-RPT and BIMI
- The website: its title, host and CDN
- Tech stack: its server software, backend, framework, CMS and plugins, UI and CSS libraries, fonts and build tools, with versions where the site gives them away, each checked for end of life (endoflife.date) and known vulnerabilities (OSV); how the page is rendered and cached; and the code it loads from other sites (public CDNs, pinned versions, integrity checks, compromised or unregistered domains)
- AI and agents: which AI crawlers robots.txt lets in and which AI products (ChatGPT search, Claude, Perplexity, Google's AI Overviews, Copilot…) can cite the site; what an agent reads there (text without JavaScript, Markdown on request, llms.txt, structured data); and what it can call (MCP servers, API catalogs, agent skills, shopping through UCP, WebMCP tools)
- HTTPS: the certificate, a grade for the security headers, HSTS, HTTP/3, ECH, CAA, security.txt, redirects and the response headers
- Exposure: open ports, software and possible CVEs, from Shodan InternetDB
- In a browser, also the route there, traced live through each network and exchange, and latency measured from the visitor's browser

A network (AS number) report covers its prefixes and address space, RPKI and ASPA records, upstreams and peers, internet exchanges and peering policy, and its registration.

Where the data comes from:

- Looked up live: DNS over HTTPS from Cloudflare's 1.1.1.1, RDAP and WHOIS, the site itself (its front page and response headers, a Markdown version, robots.txt, llms.txt, security.txt and the files it publishes for agents under /.well-known/), Certificate Transparency via Cert Spotter, Cloudflare Radar, Shodan InternetDB, hstspreload.org, endoflife.date and OSV
- Mirrored hourly: the bgp.tools routing table and network names, RPKI records from rpki-client, and the official MCP Registry
- Mirrored daily: cloud, CDN and crawler address ranges, iCloud Private Relay and Tor exits, PeeringDB, and ASPA records
- Mirrored twice a week: MaxMind GeoLite2 locations
- From the visitor's browser: traceroutes with Globalping, and latency

Every lookup's URL answers in four formats:

- HTML, for browsers.
- Markdown, when the request's Accept header prefers `text/markdown`: `curl -H "Accept: text/markdown" https://heade.rs/github.com`
- Plain text, for curl, wget, HTTPie and xh: `curl https://heade.rs/github.com`
- JSON, at `/api/<query>`: `curl https://heade.rs/api/github.com`

There are no .md URLs: https://heade.rs/example.md looks up the domain example.md (.md is Moldova's top-level domain), so ask for Markdown with the Accept header.

heade.rs is also an MCP server, at https://heade.rs/mcp (Streamable HTTP, no sign-in). Its one tool, lookup, takes a domain, IP address, AS number or URL and returns the Markdown report (or the JSON). An agent skill, https://heade.rs/.well-known/agent-skills/heade-rs/SKILL.md, says when and how to use heade.rs from a shell.

Lookups are limited to 30 a minute per client. heade.rs is free and needs no account. It's made by Colin Armstrong (https://armstr.ng).

## Try it

- [heade.rs](https://heade.rs/heade.rs): a domain
- [heade.rs as JSON](https://heade.rs/api/heade.rs)
- [armstr.ng](https://heade.rs/armstr.ng): a domain
- [armstr.ng as JSON](https://heade.rs/api/armstr.ng)
- [github.com](https://heade.rs/github.com): a domain
- [github.com as JSON](https://heade.rs/api/github.com)
- [1.1.1.1](https://heade.rs/1.1.1.1): an IP address
- [1.1.1.1 as JSON](https://heade.rs/api/1.1.1.1)
- [AS13335](https://heade.rs/AS13335): a network
- [AS13335 as JSON](https://heade.rs/api/AS13335)
- [Live lookups](https://heade.rs/api/activity): the latest lookups, and the most looked-up names of the past 7 days, as JSON

## For agents

- [MCP server](https://heade.rs/mcp): Streamable HTTP; add it with `claude mcp add --transport http heade-rs https://heade.rs/mcp`. Its server card is https://heade.rs/mcp/server-card
- [Agent skill](https://heade.rs/.well-known/agent-skills/heade-rs/SKILL.md): when to use heade.rs and how to call it, listed in https://heade.rs/.well-known/agent-skills/index.json
- [OpenAPI description](https://heade.rs/openapi.json): the JSON API, also listed in the API catalog at https://heade.rs/.well-known/api-catalog
- [AI Catalog](https://heade.rs/.well-known/ai-catalog.json): all of the above in one file

## Optional

- [Usage](https://heade.rs/help): the commands for a terminal, as plain text (or Markdown, when asked)
- [Colin Armstrong](https://armstr.ng): who made heade.rs, the founder and CEO of Paragraph