Availability checks
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/137.0.0.0 Safari/537.36 NorthDuty/1.0 (+https://northduty.com/docs/monitoring-ips) — a lightweight request that fetches the HTML and nothing else.
Monitoring IPs and user agents
NorthDuty checks identify themselves on every request. This page lists the address and user agents they come from, so you can allowlist them in a firewall, WAF, or security plugin.
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Where checks come from
Every NorthDuty check — availability checks, full health checks, and user journeys — originates from a single address: 52.206.207.60. If you allowlist one thing, allowlist that.
Checks are read-only by default. They request pages the way a visitor's browser would, and they do not submit forms, place orders, or sign in unless you have configured a user journey that does so with credentials you supplied.
How to recognise a NorthDuty request
Three user agents, depending on which check is running. All of them come from the address above.
Full health checks, screenshots and journeys
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/137.0.0.0 Safari/537.36 — a real Chromium browser, which is why it presents a standard browser user agent and executes your page the way a visitor would.
robots.txt lookups
NorthDuty-Bot/1.0 — used only to read robots.txt before checking a site.
Allowlisting NorthDuty
Cloudflare: add a WAF custom rule with the expression (ip.src eq 52.206.207.60) and the action Skip, selecting all remaining custom rules, rate limiting, and managed rules. Super Bot Fight Mode blocks automated browsers even from an allowlisted address, so if you run it, add the skip rule rather than relying on the address alone.
LiteSpeed and OpenLiteSpeed: add 52.206.207.60 to the allow list under WebAdmin, Security, Access Control. If you run a bot or crawler rule that matches on user agent, make sure it does not reject requests carrying the NorthDuty token.
Wordfence and similar WordPress plugins: add 52.206.207.60 under the allowlisted IP addresses setting, and check that the rate limiting rules do not throttle it. WordPress firewalls commonly block anything that names itself in the user agent, which is exactly what our availability check does.
Anything else: allowlist the address, and exempt it from rate limiting. A monitoring check by design repeats on a schedule, and a rate limit is the most common reason an otherwise allowlisted checker is still refused.
Frequently Asked Questions
Answers to common questions about NorthDuty and website monitoring.
What happens if I do not allowlist it?
If your firewall refuses our checker but serves real visitors normally, NorthDuty reports monitoring as limited rather than reporting your site as down. Availability still counts, but page-level measurements — load time, JavaScript errors, failed requests, layout stability — are excluded, because the page we were served was your firewall's, not yours.
Does NorthDuty ignore robots.txt?
NorthDuty reads robots.txt before checking a site. Monitoring checks the pages you have explicitly asked it to check, which is a different activity from crawling, but robots.txt is still fetched and recorded.
How often will I see requests?
It depends on the schedule you set for each project. Availability checks run most frequently and are the lightest; full health checks, screenshots, and journeys run less often because each one launches a real browser.
Will the address change?
If it changes, this page is updated before the change takes effect. It is linked from the user agent of every availability check so there is always a current reference.
Start monitoring your website with NorthDuty today.
Monitoring only helps if the checks reach your site. Allowlist the address above, and NorthDuty will tell you when a page, a journey, or an API stops working.
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