What Are AI Crawlers, Which Ones Matter, and How Do You Control Access?

What are the major AI crawlers and what do they do?

Five AI crawlers account for the majority of AI-driven web indexing as of Q1 2026. Each is operated by a different company, serves a different AI product, and crawls with different frequency and depth. Understanding which crawler feeds which product is essential for controlling your AI visibility.

A critical distinction: GPTBot and OAI-SearchBot serve different functions despite both being operated by OpenAI. GPTBot collects data for model training and the general knowledge base. OAI-SearchBot collects data for real-time web search results when users use ChatGPT Browse. Blocking GPTBot but allowing OAI-SearchBot means your content cannot be used for training but can still appear in real-time ChatGPT search results.

Google-Extended is separate from Googlebot. Blocking Google-Extended does not affect your traditional Google Search rankings or indexation. It only controls whether your content is used for Gemini and Google AI Overviews training. Googlebot continues to crawl and index your pages for organic search regardless of Google-Extended settings. According to Google's own documentation published in September 2023, this separation is by design.

None of these crawlers execute JavaScript. If your website relies on client-side rendering (React, Vue, Angular without server-side rendering), AI crawlers will see an empty page or a loading skeleton. This is the single most common technical blocker for AI citations. A 2025 Wix study found that 23% of sites blocking AI citations were doing so unintentionally because their content was rendered client-side.

For technical details on making JavaScript sites accessible to AI crawlers, see Next.js AEO Optimization: Making Server-Rendered Content AI-Citable.

Should you block or allow AI crawlers?

If you want AI engines to cite your content, allow their crawlers. Blocking an AI crawler removes your content from that platform's index, which means it cannot retrieve or cite your pages. The decision is binary: allow the crawler and be eligible for citation, or block it and be invisible on that platform.

There are legitimate reasons to block AI crawlers. Publishers who monetize content directly (paywalled articles, licensed databases) may not want their content used for AI training. Blocking GPTBot prevents OpenAI from using your content for model training. Some publishers block training crawlers (GPTBot, Google-Extended) while allowing search crawlers (OAI-SearchBot, PerplexityBot) to maintain citation visibility without contributing to training datasets.

For most businesses seeking AI visibility, the recommendation is to allow all five crawlers. A Semrush analysis of 10,000 domains in late 2025 found that 38% of sites had at least one AI crawler blocked in robots.txt — and in 71% of those cases, the block was unintentional (usually a blanket disallow rule that predated AI crawlers). If your robots.txt contains broad disallow rules, audit it specifically for AI crawler impact.

The risk of allowing AI crawlers is that your content may be used for model training, which some organizations consider an intellectual property concern. This is a policy decision, not a technical one. As of Q1 2026, no court has ruled definitively on whether AI training constitutes fair use of web content. Organizations with strong concerns should consult legal counsel while allowing search-specific crawlers (OAI-SearchBot, PerplexityBot) for citation benefits.

How do you configure robots.txt for AI crawlers?

robots.txt configuration for AI crawlers follows the same syntax as traditional crawler rules. Each AI crawler is identified by its user agent string. You can allow or disallow specific crawlers independently, giving you granular control over which platforms can index your content.

To allow all AI crawlers (recommended for maximum AEO visibility), your robots.txt needs no special entries. The default behavior when a crawler is not mentioned in robots.txt is to allow access. However, check for existing blanket rules that might block them:

A common problem: many sites have a rule like "User-agent: * / Disallow: /" that blocks all non-specified crawlers. This blocks AI crawlers by default. To fix this while maintaining the blanket block for other bots, add explicit allow rules for each AI crawler above the blanket rule.

To block specific crawlers while allowing others, add targeted disallow rules. For example, to block GPTBot (training) while allowing OAI-SearchBot (real-time search), add "User-agent: GPTBot / Disallow: /" and ensure no rule blocks OAI-SearchBot. Each crawler respects only the rules under its specific user agent block or under the wildcard user agent if no specific block exists.

After updating robots.txt, verify changes within 24 to 48 hours. OpenAI provides a GPTBot checker at platform.openai.com. For other crawlers, monitor your server logs for the user agent strings listed in the table above. Log analysis confirms whether crawlers are accessing your site as expected.

For more on making your site discoverable by AI systems, see What Is llms.txt and Should Your Site Have One?.

How do you verify which AI crawlers visit your site?

Server log analysis is the definitive method for verifying AI crawler visits. Access logs record every request to your server, including the user agent string. Filter your logs for the five AI crawler user agents listed above to see crawl frequency, which pages are requested, and response codes returned.

The process requires access to raw server logs (Apache access.log, Nginx access.log, or cloud provider equivalents). Most hosting providers surface these in cPanel, Plesk, or a logging dashboard. For sites on Vercel, Netlify, or similar platforms, you may need to enable logging explicitly or use a log drain service like Datadog or Logtail.

A practical alternative for sites without easy log access: use a web analytics tool that captures bot traffic. Cloudflare's bot analytics dashboard, available on paid plans, identifies AI crawler requests specifically. It reports crawl frequency, pages visited, and response codes without requiring manual log analysis. As of late 2025, Cloudflare reports that GPTBot is the most frequent AI crawler across its network, followed by PerplexityBot and ClaudeBot.

Verification is important because robots.txt is advisory, not enforced. Crawlers honor robots.txt voluntarily. All five major AI crawlers listed in this article respect robots.txt directives, but third-party scrapers or unofficial bots may not. Log analysis confirms actual behavior, not just intended configuration. SCALEBASE recommends quarterly log audits for AI crawler activity as part of a standard AEO maintenance routine.

For AEO implementation support including technical configuration, see SCALEBASE AEO services.