The direct answer

In 2026 the major AI crawlers visiting websites are GPTBot (OpenAI/ChatGPT), PerplexityBot (Perplexity AI), Google-Extended (Google AI Overviews), ClaudeBot (Anthropic/Claude), Bingbot with AI indexing (Microsoft Copilot), OAI-SearchBot (OpenAI search), CCBot (Common Crawl, used by many AI training datasets), and DuckAssistBot (DuckDuckGo AI). Each uses a distinct user agent string and indexes content for a specific AI system or training purpose.

What each major AI crawler is looking for

GPTBot — OpenAI / ChatGPT

GPTBot indexes content for both ChatGPT’s knowledge base and for web browsing mode. It prioritizes clean, semantic HTML with clear authorship signals and factual, well-structured content. GPTBot respects robots.txt and honors explicit Allow and Disallow rules. Sites blocking GPTBot will not appear in ChatGPT web browsing results or AI Overviews powered by OpenAI systems. User agent string: GPTBot

PerplexityBot — Perplexity AI

PerplexityBot is currently one of the most citation-active AI crawlers — Perplexity’s answers heavily cite sources, making it the platform most valuable to monitor for ANI performance. It indexes content for Perplexity’s real-time answer generation. It prioritizes content freshness, clear source attribution, and structured data. User agent string: PerplexityBot

Google-Extended — Google AI Overviews

Google-Extended is a separate crawler from Googlebot. It indexes content specifically for Google’s AI training and AI Overviews (formerly Search Generative Experience). Sites can block Google-Extended without affecting traditional Google search rankings — but doing so opts them out of AI Overview citations. User agent string: Google-Extended

ClaudeBot — Anthropic / Claude

ClaudeBot indexes content for Anthropic’s Claude AI assistant. It follows robots.txt and prioritizes well-structured, credibly attributed content. As Claude’s user base grows, ClaudeBot citations become increasingly valuable for reaching professional and technical audiences. User agent string: ClaudeBot

OAI-SearchBot — OpenAI Search

OAI-SearchBot is OpenAI’s search-specific crawler, separate from GPTBot. It focuses on real-time web search results for ChatGPT’s search functionality. User agent string: OAI-SearchBot

User-agent: GPTBot
Allow: /

User-agent: PerplexityBot
Allow: /

User-agent: ClaudeBot
Allow: /

User-agent: Google-Extended
Allow: /

User-agent: OAI-SearchBot
Allow: /

User-agent: CCBot
Allow: /

User-agent: DuckAssistBot
Allow: /

What AI crawlers evaluate on each page

All major AI crawlers evaluate similar signals when visiting a page: HTML structure and semantic element usage, heading hierarchy and its relationship to content sections, structured data (schema markup) in the page head, author and organization attribution signals, content quality and depth signals, and internal link patterns that reveal site structure. The specific weighting varies by crawler but the foundational signals are consistent across all major AI systems.

How to check which crawlers have visited your site

Log into your hosting account and find Raw Access Logs or Error Logs. Download the most recent log file and open it in a text editor. Search for GPTBot, PerplexityBot, ClaudeBot, and Google-Extended. If you find them, note the frequency of visits — daily crawls indicate active indexing, while monthly or less frequent visits suggest your site has low priority in that system’s crawl queue. If you find no visits at all, check your robots.txt immediately.

How crawl frequency differs by AI system

Different AI systems crawl at very different frequencies. Perplexity crawls actively because its answers are designed to be current — it needs fresh content to provide up-to-date answers. GPTBot crawls less frequently for its knowledge base but more actively for web browsing mode. ClaudeBot crawls at a moderate frequency focused on quality over recency. Understanding these patterns helps you prioritize which crawlers to focus on for your specific content type — time-sensitive content benefits most from Perplexity indexing, while evergreen educational content benefits equally from all major crawlers.

What to do if a specific crawler is not visiting

If a specific AI crawler is not appearing in your logs after you have verified your robots.txt allows it and your security plugin is not blocking it, there are two additional steps to try. First, submit your sitemap directly to any available submission tools the AI company offers — Bing Webmaster Tools is particularly important for ChatGPT since ChatGPT’s web browsing uses Bing’s index. Second, create high-quality content and promote it actively — crawlers prioritize sites that receive external links and social signals, treating them as higher-value indexing targets. A new site with no external links may wait weeks for its first AI crawler visit even with correct technical configuration.

The relationship between traditional SEO and AI crawler access

Traditional SEO performance and AI crawler access are positively correlated. Sites that rank well in Google tend to be crawled more frequently by AI systems — Google’s crawl data is one signal AI systems use to identify high-quality content worth indexing. This means improving your traditional SEO fundamentals (page speed, clean HTML, strong internal linking, quality backlinks) also tends to improve your AI crawler access over time. ANI-specific work accelerates this by explicitly permitting AI crawlers rather than relying on the correlation to work in your favor.

Common mistakes to avoid

A common mistake is assuming that because Googlebot visits your site, all crawlers can access it. Googlebot access and AI crawler access are separate. Your robots.txt may have Googlebot-specific allow rules while blocking everything else with a broad Disallow. Check each major AI crawler user agent individually rather than relying on a general assumption of openness.

Quick implementation checklist

• Add explicit Allow: / rules for each of the 7 major AI crawlers listed in this guide
• Check security plugin settings for bot blocking rules affecting AI crawlers
• Review server logs monthly for the first 90 days after implementing allow rules
• Search your main topics in Perplexity to verify citation activity
• Submit sitemap to Bing Webmaster Tools for ChatGPT browsing coverage

How this connects to the full ANI system

Knowing which crawlers visit your site and what they look for informs every ANI decision — from robots.txt configuration to content structure choices. For the complete ANI implementation guide covering all 24 topics in sequence, see the full ANI guide at teachmeoptimization.com/ani.

Measuring improvement

After implementing the steps in this guide, revisit your server access logs in 2 to 4 weeks to confirm AI crawler visits. Run your site through the free TeachMeOptimization scanner to check your ANI score before and after. Track your AI citation rate monthly using the manual Perplexity and ChatGPT audit process described in the ANI audit guide — citation rate improvement is the ultimate measure of whether your ANI implementation is working.