Robots.txt and Sitemap Checker

---
name: robots-txt-and-sitemap-checker
description: Checks a site's robots.txt and XML sitemap offline the way Google reads them. Picks the crawler's group, resolves longest-match Allow and Disallow with wildcards, and tests the URLs that must be crawlable or blocked. Flags whole-site blocks, sitemap URLs that robots.txt blocks, blocked CSS and JS, unsupported noindex and crawl-delay lines, off-site, duplicate or invalid sitemap entries. Includes a stdlib Python checker with --self-test.
---

# Robots.txt and Sitemap Checker

You help site owners, SEO specialists and web developers make sure search engines can crawl the pages that matter and skip the ones that do not. From a robots.txt, an XML sitemap and a list of important URLs, you show which rule decides each URL, find contradictions between robots.txt and the sitemap, explain each problem in plain words and propose a corrected robots.txt and sitemap fixes.

## Files in this skill

- `scripts/crawl_check.py` - parses robots.txt and a sitemap, decides allowed or blocked per URL like Googlebot, and prints a URL table and findings (Python 3 standard library only, no network)
- `references/robots-txt-rules.md` - groups, longest-match and wildcard rules with examples, supported directives, common mistakes and how to test
- `references/sitemap-rules-and-fixes.md` - sitemap format and limits, what to list, lastmod, and the fix for each finding
- `templates/crawl-audit-report.md` - an audit report with a proposed robots.txt to hand to the developer
- `examples/outdoor-shop-crawl-check.json` - an outdoor gear shop after a relaunch: blog and JS blocked by mistake, a noindex line, an open admin path, and a sitemap with a blocked, an off-site, a duplicate and badly dated URLs

## Workflow

### 1. Collect the files
Ask for the live robots.txt (`https://<host>/robots.txt`), the sitemap or sitemap index, the canonical origin (scheme and host), and two short lists: URLs that must be crawlable (home, categories, top products or articles, CSS/JS bundles) and URLs that should be blocked (cart, checkout, internal search, filters, admin). Ask which crawler matters most (default Googlebot).

### 2. Run the checker
```
python3 scripts/crawl_check.py examples/outdoor-shop-crawl-check.json --today 2026-10-23
python3 scripts/crawl_check.py --robots robots.txt --sitemap sitemap.xml --site https://www.example.com --allow /product/x --block /cart/
python3 scripts/crawl_check.py --self-test
```
A bundle JSON holds the site, crawler, robots.txt and sitemap lines and the URL lists. Exit code 1 means CRITICAL or HIGH findings, 2 means bad input.

### 3. Explain and fix
Start with CRITICAL and HIGH: whole-site blocks, important pages blocked, sitemap URLs that robots.txt blocks, off-site sitemap entries. For each, name the deciding line and give the corrected rule. Explain that robots.txt does not remove pages from search or protect private pages (`references/robots-txt-rules.md`), and point to the fix table in `references/sitemap-rules-and-fixes.md`.

### 4. Deliver
Fill `templates/crawl-audit-report.md` with the URL table, findings, a full corrected robots.txt and the sitemap generator changes, then re-run the checker on the corrected files.

## Example result
For `examples/outdoor-shop-crawl-check.json` the status is HIGH: `Disallow: /blog/` (line 9) blocks /blog/trail-running-shoes-review and the listed /blog/spring-sale-recap, `Disallow: /assets/js/` blocks the app bundle, and http://trailgear.example/backpacks/ in the sitemap is off-site. The `Noindex: /search/` line is ignored by Google, so /search/ and /admin/ stay crawlable; the sitemap also has a duplicate /tents/, a lastmod in 2027 and one in `18.10.2026` format.

## Rules

- Always name the exact robots.txt line that decides a URL, and the crawler it was evaluated for.
- Never suggest robots.txt to hide private or sensitive pages; use authentication, and `noindex` for pages that must stay out of search.
- Give a complete corrected robots.txt, not only fragments, and keep rules the owner added on purpose (for example blocking AhrefsBot).
- The checker does not fetch URLs; say that status codes, redirects, canonicals and noindex tags need a crawl or Search Console.
FILE:references/robots-txt-rules.md
# robots.txt Rules (RFC 9309 and Google)

## Where and what
- Lives at the root of each host and protocol: `https://www.example.com/robots.txt` covers only that host. `example.com`, `shop.example.com` and `http://` need their own file.
- Plain text, UTF-8. Google reads the first 500 KiB. A 404 means "everything allowed"; a 5xx for a long time can make Google stop crawling the site.
- robots.txt controls **crawling**, not indexing. A blocked URL can still appear in search (without a snippet) if other pages link to it. To keep a page out of search, allow crawling and send `noindex`; to keep it private, require a login.

## Groups
```
User-agent: Googlebot
User-agent: Bingbot
Disallow: /tmp/

User-agent: *
Disallow: /cart/
```
- Consecutive `User-agent` lines share one group. Rules belong to the group above them.
- A crawler uses only **one** group: the one with the most specific matching name (`googlebot-image` over `googlebot`), otherwise `*`. Rules from `*` are not added to a named group, so a common mistake is a `Googlebot` group that forgets to repeat the `*` rules.
- Groups with the same name are merged.

## Matching
- Paths are case-sensitive and match from the start of the path (including the query string).
- `*` matches any characters; `$` anchors the end of the URL.
- The **longest** matching rule wins; on equal length `Allow` wins. No matching rule means allowed.
- `Disallow:` with an empty value allows everything.

| Rule | Blocks | Does not block |
|---|---|---|
| `Disallow: /shop` | /shop, /shop/, /shopping | /Shop |
| `Disallow: /shop/` | /shop/shoes | /shop |
| `Disallow: /*?sort=` | /tents/?sort=price | /tents/?color=red&sort=price (needs `/*sort=`) |
| `Disallow: /*.pdf$` | /docs/a.pdf | /docs/a.pdf?v=2 |
| `Disallow: /blog/` + `Allow: /blog/guides/` | /blog/news | /blog/guides/x |

## Directives
| Directive | Google | Notes |
|---|---|---|
| user-agent, allow, disallow | yes | core rules |
| sitemap | yes | absolute URL, any number, outside groups |
| crawl-delay | no | Bing and Yandex honour it; for Google, lower the crawl rate via server responses (429/503) |
| noindex, nofollow | no (dropped 2019) | use `<meta name="robots" content="noindex">` or the `X-Robots-Tag` header |
| host, clean-param | no | Yandex only |

## Common mistakes
- `Disallow: /` left over from staging after a launch (the whole site disappears from crawling).
- Blocking CSS, JS or image folders: Google renders pages and needs them; blocked assets can make pages look broken or not mobile-friendly.
- Blocking a page that carries `noindex`: the crawler never sees the noindex, so the URL can stay in the index.
- Using robots.txt to hide admin or private pages: the file is public and lists exactly where they are.
- Faceted URLs (sort, filter, session ids) left open, wasting crawl budget on endless combinations.
- Typos (`Disalow`) are silently ignored.

## Testing
- Google Search Console: robots.txt report (fetch status and parsed rules) and URL Inspection (blocked or not).
- Locally: `python3 scripts/crawl_check.py --robots robots.txt --site https://www.example.com --allow /product/x --block /cart/`.
FILE:references/sitemap-rules-and-fixes.md
# XML Sitemap Rules and Fixes

## Format
```xml
<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <url>
    <loc>https://www.example.com/tents/ultralight-2p</loc>
    <lastmod>2026-10-18T09:30:00+03:00</lastmod>
  </url>
</urlset>
```
- At most **50,000 URLs** and **50 MB** uncompressed per file. Larger sites use a sitemap index (`<sitemapindex>` with `<sitemap><loc>` entries), up to 50,000 sitemaps.
- UTF-8, entity-escape `&`, `<`, `>`, `'`, `"` inside `<loc>`.
- `<loc>` must be absolute, on the same protocol and host as the sitemap (unless cross-submitted through Search Console for a verified host).

## What to list
- Only canonical, indexable URLs that return 200: no redirects, no 404s, no `noindex` pages, no URLs blocked by robots.txt, no parameter duplicates.
- The exact canonical form: same scheme (https), same host (www or not), same trailing-slash style as the `rel=canonical` tag.
- Each URL once.

## lastmod
- W3C datetime: `2026-10-18`, `2026-10-18T09:30+03:00` or `2026-10-18T06:30:00Z`. Formats like `18.10.2026` or `10/18/2026` are invalid.
- Set it to the last **meaningful** content change, not the build time. Google uses lastmod only when it is consistently accurate; future dates or every URL changing every day teach it to ignore the field.
- `<changefreq>` and `<priority>` are ignored by Google; they do no harm but are not worth maintaining.

## Telling crawlers about the sitemap
- `Sitemap: https://www.example.com/sitemap.xml` in robots.txt (absolute URL).
- Submit in Google Search Console and Bing Webmaster Tools, then watch the "Discovered" and "Indexed" counts and errors.

## Fixes by finding
| Finding | Fix |
|---|---|
| SITEMAP_URL_BLOCKED | Decide: if the page should rank, remove the Disallow; if not, drop it from the sitemap |
| SITEMAP_OFF_SITE | Rewrite `<loc>` to the canonical scheme and host; check the generator's base URL setting |
| SITEMAP_DUPLICATE | Deduplicate in the generator (often category + tag listings of the same page) |
| LASTMOD_INVALID / LASTMOD_FUTURE | Output ISO 8601 from the content's updated-at field; check server time zone and clock |
| SITEMAP_TOO_BIG | Split by section or date into several files under one sitemap index |
| SITEMAP_PARSE_ERROR | Escape `&` in URLs, remove a BOM or HTML error pages served instead of XML, check the namespace |

## Beyond this checker
The script works offline on the files you give it. Also check, with a crawler or Search Console: status codes of listed URLs, redirects, canonical tags, noindex tags and hreflang alternates.
FILE:templates/crawl-audit-report.md
# Crawl Audit - <site> - <date>

**Checked:** robots.txt (<fetched on / version>), <sitemap URL(s)>  **Crawler:** <Googlebot>  **Reviewer:** <name>

## Summary
- Status: <CRITICAL / HIGH / OK>
- robots.txt: <n> groups, <n> rules for <crawler>
- Sitemap: <n> URLs, <n> blocked, <n> off-site, <n> duplicates

## Important URLs
| URL | Should be | Result | Deciding rule | Fix |
|---|---|---|---|---|
| | crawlable | | | |
| | blocked | | | |

## Findings and fixes
| Severity | Finding | Detail | Fix | Owner |
|---|---|---|---|---|
| | | | | |

## Proposed robots.txt
```
User-agent: *
Disallow: ...
Allow: ...

Sitemap: https://...
```

## Follow-up
- Deploy the new robots.txt and sitemap on <date>; test in Search Console (robots.txt report, URL Inspection)
- Recheck coverage and crawl stats on <date>
FILE:examples/outdoor-shop-crawl-check.json
{
  "site": "https://www.trailgear.example",
  "user_agent": "Googlebot",
  "robots_txt": [
    "# robots.txt for www.trailgear.example (after the October relaunch)",
    "User-agent: *",
    "Disallow: /cart/",
    "Disallow: /checkout/",
    "Disallow: /account/",
    "Disallow: /*?sort=",
    "Disallow: /*?sessionid=",
    "Disallow: /assets/js/",
    "Disallow: /blog/",
    "Allow: /blog/guides/",
    "Crawl-delay: 10",
    "Noindex: /search/",
    "",
    "User-agent: AhrefsBot",
    "Disallow: /",
    "",
    "Sitemap: https://www.trailgear.example/sitemap.xml"
  ],
  "sitemap_xml": [
    "<?xml version=\"1.0\" encoding=\"UTF-8\"?>",
    "<urlset xmlns=\"http://www.sitemaps.org/schemas/sitemap/0.9\">",
    "  <url><loc>https://www.trailgear.example/</loc><lastmod>2026-10-20</lastmod></url>",
    "  <url><loc>https://www.trailgear.example/tents/</loc><lastmod>2026-10-18</lastmod></url>",
    "  <url><loc>https://www.trailgear.example/tents/ultralight-2p</loc><lastmod>2026-10-18T09:30:00+03:00</lastmod></url>",
    "  <url><loc>https://www.tr

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