SEO Technical: robots.txt
Guides configuration and auditing of robots.txt for search engine and AI crawler control.
When invoking: On first use, if helpful, open with 1–2 sentences on what this skill covers and why it matters, then provide the main output. On subsequent use or when the user asks to skip, go directly to the main output.
Scope (Technical SEO)
- Robots.txt: Configure Disallow/Allow, Sitemap, Clean-param; audit for accidental blocks
- Crawler access: Path-level crawl control; AI crawler allow/block strategy
- Differentiation: robots.txt = crawl control (who accesses what paths); noindex = index control (what gets indexed). See indexing for page-level exclusions.
Initial Assessment
Project context: Read root contextus.md when present and load only the modules relevant to this task. Without Contextus, use available project material or user-provided facts and ask for missing information; do not create a parallel context system.
Identify:
- Site URL: Base domain (e.g.,
https://example.com) - Indexing scope: Full site, partial, or specific paths to exclude
- AI crawler strategy: Allow search/indexing vs. block training data crawlers
Best Practices
Purpose and Limitations
| Point | Note |
|---|---|
| Purpose | Controls crawler access; does NOT prevent indexing (disallowed URLs may still appear in search without snippet) |
| Advisory | Rules are advisory; malicious crawlers may ignore |
| Public | robots.txt is publicly readable; use noindex or auth for sensitive content. See indexing |
Crawl vs Index vs Link Equity (Quick Reference)
| Tool | Controls | Prevents indexing? |
|---|---|---|
| robots.txt | Crawl (path-level) | No—blocked URLs may still appear in SERP |
| noindex (meta / X-Robots-Tag) | Index (page-level) | Yes. See indexing |
| nofollow | Link equity only | No—does not control indexing |
When to Use robots.txt vs noindex
| Use | Tool | Example |
|---|---|---|
| Path-level (whole directory) | robots.txt | Disallow: /admin/, Disallow: /api/, Disallow: /staging/ |
| Page-level (specific pages) | noindex meta / X-Robots-Tag | Login, signup, thank-you, 404, legal. See indexing for full list |
| Critical | Do NOT block in robots.txt | Pages that use noindex—crawlers must access the page to read the directive |
Paths to block in robots.txt: /admin/, /api/, /staging/, temp files. Paths to use noindex (allow crawl): /login/, /signup/, /thank-you/, etc.—see indexing.
Location and Format
| Item | Requirement |
|---|---|
| Path | Site root: https://example.com/robots.txt |
| Encoding | UTF-8 plain text |
| Standard | RFC 9309 (Robots Exclusion Protocol) |
Core Directives
| Directive | Purpose | Example |
|---|---|---|
User-agent: |
Target crawler | User-agent: Googlebot, User-agent: * |
Disallow: |
Block path prefix | Disallow: /admin/ |
Allow: |
Allow path (can override Disallow) | Allow: /public/ |
Sitemap: |
Declare sitemap absolute URL | Sitemap: https://example.com/sitemap.xml |
Clean-param: |
Strip query params (Yandex) | See below |
Path Format Rules (Critical)
Different directives use different path formats — a common source of errors:
| Directive | Format | Correct | Wrong |
|---|---|---|---|
| Disallow / Allow | Root-relative path only (starts with /) |
Disallow: /admin/ |
Disallow: https://example.com/admin/ |
| Sitemap | Absolute URL only | Sitemap: https://example.com/sitemap.xml |
Sitemap: /sitemap.xml |
Wildcards: * matches any character sequence (Disallow: /tmp/*). $ marks exact URL ending (Allow: /news/.html$).
Priority: More specific paths take precedence. Allow: /shop/shoes/ overrides Disallow: /shop/. Path matching is case-sensitive: Disallow: /PDF/ does not match /pdf/.
Critical: Do Not Block
| Do not block | Reason |
|---|---|
| CSS, JS, images | Google needs them to render pages; blocking breaks indexing |
/_next/ (Next.js) |
Breaks CSS/JS loading; static assets in GSC "Crawled - not indexed" is expected. See indexing |
| Pages that use noindex | Crawlers must access the page to read the noindex directive; blocking in robots.txt prevents that |
Only block: paths that don't need crawling: /admin/, /api/, /staging/, temp files.
AI Crawler Strategy
robots.txt is effective for all measured AI crawlers. Set rules per user-agent; check each vendor's docs for current tokens.
| User-agent | Purpose | Typical | Notes |
|---|---|---|---|
| OAI-SearchBot | ChatGPT search | Allow | Respects robots.txt |
| GPTBot | OpenAI training | Disallow | Respects robots.txt; shares crawl data with OAI-SearchBot if both allowed |
| ChatGPT-User | User-initiated browsing | N/A | No longer respects robots.txt (Dec 2025); use server-side controls instead |
| Claude-SearchBot | Claude search | Allow | Respects robots.txt |
| Claude-User | Anthropic user-initiated browsing | Allow | Respects robots.txt (unlike ChatGPT-User) |
| ClaudeBot | Anthropic training | Disallow | Respects robots.txt |
Deprecated:
anthropic-ai— retired by Anthropic, replaced by ClaudeBot / Claude-User / Claude-SearchBot. References toanthropic-aiin robots.txt have no effect. | PerplexityBot | Perplexity search | Allow | Respects robots.txt | | Google-Extended | Gemini training | Disallow | Respects robots.txt | | CCBot | Common Crawl (LLM training) | Disallow | Respects robots.txt | | Bytespider | ByteDance | Disallow | Respects robots.txt | | Meta-ExternalAgent | Meta | Disallow | Respects robots.txt | | AppleBot | Apple (Siri, Spotlight); renders JS | Allow for indexing | Respects robots.txt |
Allow vs Disallow: Allow search/indexing bots (OAI-SearchBot, Claude-SearchBot, PerplexityBot); Disallow training-only bots (GPTBot, ClaudeBot, CCBot) if you don't want content used for model training.
Important — ChatGPT-User exemption: As of December 2025, ChatGPT-User no longer respects robots.txt directives. OpenAI considers it a proxy for human-initiated browsing. If you need to block it, use server-side controls (WAF rules, IP rate-limiting), not robots.txt. See site-crawlability for AI crawler optimization (SSR, URL management).
Clean-param (Yandex)
Clean-param: utm_source&utm_medium&utm_campaign&utm_term&utm_content&ref&fbclid&gclid
Output Format
- Current state (if auditing)
- Recommended robots.txt (full file)
- Compliance checklist
- References: Google robots.txt
Related Skills
- indexing: Full noindex page-type list; when to use noindex vs robots.txt; GSC indexing diagnosis
- page-metadata: Meta robots (noindex, nofollow) implementation
- xml-sitemap: Sitemap URL to reference in robots.txt
- site-crawlability: Broader crawl and structure guidance; AI crawler optimization
- rendering-strategies: SSR, SSG, CSR; content in initial HTML for crawlers