The direct answer

The AI crawler user agents you should allow in robots.txt in 2026 are: GPTBot (OpenAI/ChatGPT), PerplexityBot (Perplexity AI), ClaudeBot (Anthropic/Claude), Google-Extended (Google AI Overviews and training), OAI-SearchBot (OpenAI search feature), CCBot (Common Crawl, used by many AI training datasets), and DuckAssistBot (DuckDuckGo AI). This list reflects the major AI systems with significant user bases as of 2026 and should be reviewed quarterly as new AI systems emerge.

The complete user agent reference for 2026

Why you need explicit allow rules rather than relying on defaults

Many site owners assume that a robots.txt file with no Disallow rules means all crawlers are welcome. This is technically correct — but security plugins, server-level firewall rules, and CDN bot protection settings can override robots.txt independently. Explicit allow rules for each AI crawler create a documented record of your crawl policy that can also be referenced when troubleshooting why a specific AI crawler is not visiting despite robots.txt appearing to allow it.

How to stay current as new AI crawlers emerge

The AI search landscape changes rapidly. New AI systems launch, existing systems add new crawlers, and user agent strings occasionally change. Review your robots.txt quarterly — the same schedule as your content map review and your ANI audit. Check your server access logs monthly for any unfamiliar user agent strings and research whether they are legitimate AI crawlers worth explicitly allowing. The quickest way to identify new AI crawlers is to search for the user agent string you find in your logs.

How to identify new AI crawler user agents as they emerge

When you review your server access logs, occasionally you will see unfamiliar user agent strings that do not match any crawler you recognize. Before blocking them, search the exact user agent string to identify whether it is a legitimate AI crawler, a traditional SEO tool, or an actual malicious bot. Legitimate AI company crawlers will have documentation published by their parent company. If you cannot find any documentation for a user agent string, treat it cautiously — but do not block strings preemptively without identifying them.

The distinction between AI crawlers and AI training scrapers

Some crawlers index content for real-time AI answer generation (GPTBot browsing mode, PerplexityBot) while others collect content for AI model training datasets (CCBot, some uses of GPTBot). The robots.txt convention treats these distinctly — you can allow real-time indexing crawlers while blocking training dataset scrapers if you prefer your content not be used for AI model training. CCBot, which powers Common Crawl used in many AI training datasets, can be specifically blocked if this is a concern. However for most site owners building visibility in AI search, allowing all legitimate AI crawlers including CCBot is the recommended approach.

Verifying your allow rules are working

After adding allow rules to robots.txt, verify they are working correctly by using Google’s robots.txt testing tool in Search Console (Settings > robots.txt) or the standalone tool at search.google.com/search-console/robots-testing-tool. While this tool is designed for Googlebot, the same rules apply to AI crawlers — if your allow rules are correctly structured for Googlebot they will work correctly for AI crawlers following the same robots.txt conventions. Test with a specific page URL and the GPTBot user agent to confirm the allow rule is being applied correctly.

Common mistakes to avoid

A common mistake is treating the user agent list as permanent. New AI systems launch regularly and existing systems add new crawlers. Set a quarterly reminder to review your robots.txt user agent list alongside your broader ANI audit. Check your server logs for any unfamiliar user agent strings that appear to be AI crawlers and research them before deciding to allow or block them.

Quick implementation checklist

• Add all 7 user agents from the reference table to your robots.txt
• Set a quarterly calendar reminder to review and update the user agent list
• Check server logs monthly for unfamiliar user agent strings
• Research any unfamiliar user agents before blocking them
• Verify the allow rules are working using Google’s robots.txt testing tool

How this connects to the full ANI system

The user agent list is your primary tool for controlling which AI systems can index your content. Keeping it current ensures your site benefits from new AI systems as they emerge rather than remaining invisible to them by default. 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.