What is Let's Encrypt?

Only if no one on your team relies on it. Let's Encrypt may support uptime monitoring, performance tests, or audits. Blocking it without checking first can silently disrupt those workflows. For context, 6% of the top websites we track currently have robots.txt rules for Let's Encrypt.

No. Let's Encrypt is not expected to follow robots.txt rules, so a disallow rule only communicates your preference. Enforce the block with firewall or server rules, then use Agent Analytics to verify that its requests stop.

Only when configured with access. A team may grant Let's Encrypt credentials to monitor staging sites or private health endpoints. Without those credentials, it sees only public pages.

Agent Analytics tracks Let's Encrypt visits in real time. You can also check your server logs for requests whose user-agent string contains "Let's Encrypt". Look for repeated checks of the same pages or endpoints at regular intervals. Because Let's Encrypt does not publish a verification method, any client can claim its identity and a log match is only a clue.

Someone, most likely on your own team, configured Let's Encrypt to check your site. Uptime monitors, performance testers, and audit tools visit only the sites or endpoints they are told to watch.