Cloudflare will crawl your site when you have specific products enabled:

• Always Online
  • User-Agent:Mozilla/5.0 (compatible; CloudFlare-AlwaysOnline/1.0; +http://www.cloudflare.com/always-online)
• Health checks
  • User-Agent:Mozilla/5.0 (compatible; Cloudflare-Healthchecks/1.0; +https://www.cloudflare.com/; healthcheck-id: <HEALTHCHECK_ID>)
  • HEALTHCHECK_ID is a 16-character string associated with the health check ID.
• Load balancing monitors
  • User-Agent:Mozilla/5.0 (compatible; Cloudflare-Traffic-Manager/1.0; +https://www.cloudflare.com/traffic-manager/; pool-id: <POOL_ID>)
  • POOL_ID is a 16-character string associated with the load balancing pool ID being monitored.
• Prefetch URLs
  • User-Agent:Mozilla/5.0 (compatible; CloudFlare-Prefetch/0.1; +http://www.cloudflare.com/)
• SSL/TLS recommender
  • User-Agent:Cloudflare-SSLDetector
  • This crawler ignores yourrobots.txt file unless there are rules explicitly targeting the user agent.
• Security Insights
  • User-Agent:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.107 Safari/537.36 (compatible; +https://developers.cloudflare.com/security-center/)

Cloudflare will also crawl your site in other, specific situations:

• Speed tests
  • User-Agent:Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/75.0.3770.100 Safari/537.36 PTST/190628.140653
  • Triggered when: You launch a speed test from withinthe Cloudflare dashboard.
• Support diagnostics:
  • User-Agent:Cloudflare-diagnostics
  • Triggered when: Cloudflare Support Engineers perform error checks and by continuous monitoring used to raise intelligent alerts in the Cloudflare dashboard.
• Custom Hostname validation:
  • User-Agent:Cloudflare Custom Hostname Verification
  • Triggered when: You choose to validate a custom hostname with anHTTP ownership token.