Crawler
An automated program that discovers and indexes web pages (also called a spider or bot).
Key takeaways
- Crawler is an automated program that discovers and indexes web pages (also called a spider or bot).
- Check what each crawler receives by requesting key pages with its user agent.
- Avoid: assuming every crawler renders JavaScript like Googlebot.
What is Crawler?
Major crawlers include Googlebot, Bingbot, GPTBot and PerplexityBot. Each respects robots.txt. AI crawlers are increasingly important for AEO visibility.
Google lists its own crawlers and their user agents in its overview of Google crawlers.
Why Crawler matters for SEO in 2026
Crawlers decide what search engines and AI assistants can know about your site. Many AI crawlers don't run JavaScript, so a page that only renders in the browser can be invisible to them even if Google sees it.
For a wider view of where this fits, see our full SEO glossary or explore the SEO and GEO service we run for clients.
How to apply Crawler on your site
Knowing the concept is only half of it. Work through these steps in order to put Crawler into practice on your own pages:
- Check what each crawler receives by requesting key pages with its user agent.
- Serve real HTML for public pages through server rendering or pre-rendering.
- Allow the crawlers you want in robots.txt and in any firewall or bot protection.
Common mistakes to avoid
Most sites that struggle with Crawler fall into the same traps. Check your pages against each of these before moving on:
- Assuming every crawler renders JavaScript like Googlebot.
- Letting bot protection block legitimate search and AI crawlers.
- Never checking server logs to see which crawlers visit.
Questions about Crawler
An automated program that discovers and indexes web pages (also called a spider or bot).
Crawlers decide what search engines and AI assistants can know about your site. Many AI crawlers don't run JavaScript, so a page that only renders in the browser can be invisible to them even if Google sees it.
Start here: check what each crawler receives by requesting key pages with its user agent. Then serve real HTML for public pages through server rendering or pre-rendering.
The most common is assuming every crawler renders JavaScript like Googlebot. Another is letting bot protection block legitimate search and AI crawlers.