crawlerpeek

Check whether AI crawlers can access your site. For each bot (GPTBot, OAI-SearchBot, ChatGPT-User, ClaudeBot, Claude-SearchBot, PerplexityBot, Google-Extended, Googlebot, Bingbot, CCBot and more) it tells you:

• whether robots.txt allows the URL's path for that bot (RFC 9309: user-agent groups, wildcards, $, longest match wins), and
• what the page actually returns when fetched with that bot's user-agent string: status, final URL after redirects, content type, size, title, and whether the response looks like a block or challenge page.

It also lints a robots.txt for mistakes, checks every URL in a sitemap against robots.txt, and generates a robots.txt that welcomes AI crawlers. A library, a CLI for CI, and an MCP server. Node 20 or newer, no runtime dependencies, ESM and CommonJS, TypeScript types included.

The same checks as a web tool: crawlerpeek.com. Documentation with examples for CI and MCP clients: crawlerpeek.com/cli.

Install

npm install crawlerpeek       # library
npx crawlerpeek --help        # CLI, no install needed

CLI

npx crawlerpeek check https://example.com

https://example.com
robots.txt: ok (HTTP 200) at https://example.com/robots.txt

Bot                 robots    HTTP
GPTBot              blocked   200  FAIL
ClaudeBot           allowed   403 (block page)  FAIL
Google-Extended     allowed   -

npx crawlerpeek check https://example.com/pricing --bots GPTBot,ClaudeBot --fail-on blocked
npx crawlerpeek check https://example.com --bots all --json
npx crawlerpeek check https://example.com --no-http          # robots.txt only
npx crawlerpeek see https://example.com --bot ClaudeBot      # one bot, full detail
npx crawlerpeek verify 66.249.66.1 --bot Googlebot          # is this IP really Googlebot?
npx crawlerpeek lint https://example.com                     # find mistakes in its robots.txt (or: lint ./robots.txt, lint -)
npx crawlerpeek scan https://example.com --limit 50          # robots.txt per bot for the URLs in its sitemap
npx crawlerpeek check https://example.com --markdown         # GitHub-flavoured Markdown table
npx crawlerpeek robots --disallow /admin/,/cart/ --sitemap https://example.com/sitemap.xml

Exit codes: 0 ok, 1 the --fail-on condition was met, 2 usage error (including an unknown option) or request error. see exits 0 when the page was fetched, whatever its HTTP status, and 2 when the request failed or was refused.

verify <ip> [--bot GPTBot] [--json] checks whether an address from your server logs really belongs to a crawler. It uses only what the operator documents: the published IP-range JSON (Google, OpenAI, Anthropic, Perplexity, Bing, Apple, Common Crawl, DuckDuckGo, Ahrefs) or reverse DNS with forward confirmation (Google, Bing, Apple, Common Crawl, Ahrefs). Without --bot every bot with such a method is checked. Each result has method (ip-list, reverse-dns or none), verified (true, false, or null when it cannot be decided, for example the list is unreachable or the operator documents no method) and a detail. Lists are cached for one hour, and nothing is ever sent to the IP. Exit codes: 0 verified for at least one bot, 1 not verified or undecidable, 2 usage error.

check --markdown prints the result as a GitHub-flavoured Markdown table (a heading with the URL, a ✅/❌ summary line and one row per bot) instead of the text table; it cannot be combined with --json. --summary-file <path> appends the same Markdown to a file in addition to the normal output, which is how the GitHub Action fills the job summary (--summary-file "$GITHUB_STEP_SUMMARY").

lint <url|file|-> [--fail-on error|warning] [--json] checks a robots.txt: the /robots.txt of a URL, a local file, or - for stdin. It prints one line per finding (L12 warning unknown-field ...) and a summary. Each finding has a stable code, a severity (error, warning, info) and the line number, and is based on RFC 9309 or Google's robots.txt documentation:

| Code | Severity | Finding | | --- | --- | --- | | html-instead-of-robots | error | the server answered /robots.txt with a web page | | not-text | error | the file is binary or compressed data, not text | | rule-before-user-agent | warning | Allow or Disallow before any User-agent line (ignored) | | unknown-field, missing-colon | warning | a misspelled field such as Dissallow (with a "did you mean" hint), or a line without : | | path-not-absolute | warning | an Allow or Disallow path that does not start with / or * | | sitemap-not-absolute | warning | a Sitemap value that is not an absolute http(s) URL | | all-ai-blocked | warning | every AI training, search and user crawler in the default list is blocked from / | | too-large | warning | more than 500 KiB; Google reads only the first 500 KiB | | unsupported-directive | info | Crawl-delay (Google ignores it), Noindex, Host, Clean-param (not part of RFC 9309) | | extension-directive | info | Content-Signal (Cloudflare's Content Signals Policy) or License (RSL): extensions that crawlers without support skip | | unknown-agent | info | a misspelled bot token (for example GPTBott or PerplexityUser), or the legacy anthropic-ai / claude-web tokens, which are not among Anthropic's currently documented ones | | empty-group, duplicate-agent | info | a User-agent group without rules, or the same token in more than one group | | too-many-lines, findings-truncated | info | the file has more than 20 000 lines, or more than 200 findings |

Exit codes: 0 nothing at or above the --fail-on threshold (default warning), 1 findings, 2 usage error or a robots.txt that could not be fetched. A missing robots.txt (404) has no findings.

scan <url> [--limit 25] [--bots a,b|all] [--fail-on none|blocked] [--json] evaluates robots.txt for the URLs in the site's sitemap: the Sitemap: lines of its robots.txt, else /sitemap.xml; a sitemap index is followed one level (at most 5 child sitemaps). Only http(s) URLs on the same host are kept (www. and the bare domain count as different hosts, unless robots.txt redirects from one to the other), without duplicates, and --limit (1 to 200) takes the first ones. .gz sitemaps are reported as skipped. No page is fetched: the only requests are robots.txt and the sitemap files. The output has a table of how many URLs each bot is blocked from, then the blocked URLs per bot (the first 10, then "... and N more"; --json has all). Exit codes: 0 ok, 1 with --fail-on blocked when any checked bot is blocked from any URL, 2 usage or request error, or when no URL could be read from the sitemap.

| --fail-on | Fails when | | --- | --- | | blocked | robots.txt closes the path for a bot, or the page answers that bot with 401/403/406/451 or a challenge page | | any-non-200 | as above, or any other status (404, 5xx, redirects that end elsewhere) or a failed request |

Without --fail-on the exit code is 0 whatever the result. --bots takes tokens or all; the default is 15 bots: the main AI crawlers plus Googlebot and Bingbot. A robots.txt that cannot be fetched (timeout, 5xx, a redirect that is refused or has no target) is reported as unknown, with the reason in robotsTxt.error, and never counts as blocked. Note: this deliberately differs from RFC 9309 §2.3.1.4, where crawlers treat an unreachable robots.txt (5xx) as "disallow everything" (Google does too), so a site whose robots.txt returns 5xx is effectively closed to many bots even though --fail-on blocked passes. Treat unknown as a problem to fix.

Library

import { checkAiAccess, seeAsBot, verifyBotIp, lintRobotsTxt, lintRobotsUrl, scanSite, formatMarkdown, generateRobotsTxt, failingBots } from "crawlerpeek";

const report = await checkAiAccess("https://example.com/pricing", { bots: ["GPTBot", "ClaudeBot"] });
report.bots[0].robots; // { access: "allowed", pathAllowed: true, matchedGroup: "*" }
report.bots[0].http;   // { status: 200, finalUrl, redirects, contentType, bytes, title, looksBlocked, outcome: "ok", ... }
failingBots(report, "blocked"); // ["ClaudeBot"] when it is closed or challenged

await seeAsBot("https://example.com", "PerplexityBot");

await verifyBotIp("66.249.66.1", { bot: "Googlebot" }); // [{ bot: "Googlebot", method: "ip-list", verified: true, detail, source }]

lintRobotsTxt("User-agent: *\nDissallow: /a\n"); // [{ line: 1, severity: "info", code: "empty-group", ... }, { line: 2, severity: "warning", code: "unknown-field", message: '... Did you mean Disallow?' }]
await lintRobotsUrl("https://example.com");       // { url, status, state, findings, ... }

const scan = await scanSite("https://example.com", { limit: 50, bots: ["GPTBot"] });
scan.summary.perBot; // [{ bot: "GPTBot", blocked: 3 }]
scan.urls[0];        // { url: "https://example.com/private/a", blockedFor: ["GPTBot"] }

formatMarkdown(report, failingBots(report, "blocked")); // GitHub-flavoured Markdown

generateRobotsTxt({ disallow: ["/admin/"], blockBots: ["CCBot"], sitemap: "https://example.com/sitemap.xml" });

generateRobotsTxt names each AI bot explicitly with Allow: /. Disallowed paths are repeated in that group on purpose: a bot with its own group ignores the * group.

MCP server

crawlerpeek mcp speaks the Model Context Protocol over stdio and exposes six read-only tools: check_ai_access, see_as_bot, verify_bot_ip, generate_robots_txt, lint_robots_txt (give a url or the file text) and scan_site (url, limit, bots). Results are cached for 10 minutes per call. No LLM is called; the tools only fetch the URL you give them.

<a href="https://cursor.com/install-mcp?name=crawlerpeek&config=eyJjb21tYW5kIjoibnB4IiwiYXJncyI6WyIteSIsImNyYXdsZXJwZWVrIiwibWNwIl19"><picture><source media="(prefers-color-scheme: dark)" srcset="https://cursor.com/deeplink/mcp-install-dark.svg"><img src="https://cursor.com/deeplink/mcp-install-light.svg" alt="Add crawlerpeek to Cursor" height="32"></picture></a>  

| Client | Install | | --- | --- | | Claude Code | claude mcp add --transport stdio crawlerpeek -- npx -y crawlerpeek mcp | | Claude Code (plugin: MCP server and skill) | /plugin marketplace add crawlerpeek/crawlerpeek, then /plugin install crawlerpeek@crawlerpeek | | Claude Desktop | Download crawlerpeek-<version>.mcpb from Releases and open it, or add the JSON below | | Codex | codex mcp add crawlerpeek -- npx -y crawlerpeek mcp | | VS Code | code --add-mcp '{"name":"crawlerpeek","type":"stdio","command":"npx","args":["-y","crawlerpeek","mcp"]}' | | Any other client | the JSON below |

Generic configuration (Claude Desktop, Cursor, Windsurf, Cline and others use this mcpServers shape):

{ "mcpServers": { "crawlerpeek": { "command": "npx", "args": ["-y", "crawlerpeek", "mcp"] } } }