Every monitor has a name (up to 120 characters), a type, a target, and a check interval. The type decides what a probe does and what counts as a failure.
HTTP(S)
The target is a full URL, http:// or https://, without a username or password in it (up to 2,000 characters). A probe fetches it and the result is up when the status code is one you accept, any 2xx by default.
Options:
- Keyword: the page must contain a text, or must not contain it. The match is case-sensitive and looks at the first 256 KB of the body.
- Follow redirects (up to 5), verify TLS, detect error pages, timeout 1 to 30 seconds (10 by default), IP version auto, 4 or 6.
- Dev/staging mode: 401, 403 and 404 count as up and send no alerts, for sites behind a login or not yet public.
- Certificate warning: a warning, not an outage, when the certificate expires in fewer than the days you set (14 by default, up to 90). An expired certificate is an outage.
- Slow threshold: see below.
- Custom request (verified domains only): method GET, HEAD, POST, PUT, PATCH, DELETE or OPTIONS; up to 10 headers, marked secret if they carry a credential; a body of up to 10 KB as JSON, form, plain text or XML with any method except GET and HEAD; basic auth. Secret headers and passwords are stored encrypted and never shown again. A write method asks you to confirm that you mean it.
TLS certificate
Host and port. The probe opens a TLS connection and checks the certificate chain and expiry, with the same warning days as above. For mail servers it can use SMTP STARTTLS.
TCP port
Host and port. Up when the port accepts a connection. Available on verified domains.
SMTP server
Host and port, 587 by default. Up when the server greets with a 220 line. You can add the banner text you expect; if it is missing the monitor shows a warning, not an outage. Probe providers block port 25 outbound, and some also block 465 and 587, so a port is refused when too few probes could reach it. Available on verified domains.
DNS server
Host (the server to ask), a name to query, and a record type: A, AAAA, CNAME, MX, NS, SOA or TXT. Port 53 by default. Available on verified domains.
Ping (ICMP)
Host. Every 5 minutes at the fastest on an account that has not bought credits, every minute after a purchase.
Heartbeat
The opposite direction: your cron job or script calls a URL we give you, and the monitor goes down when no call arrives within the period you set (1 minute to 1 week) plus the delay you allow (1 minute to 1 day). Calling the URL with /fail at the end marks it down at once, and the first 300 characters of the request body become the reason. Pings are limited to 30 a minute per token. Heartbeat monitors use one credit per expected check-in, the same as a scheduled check at that interval.
Slow threshold (HTTP)
A monitor can also alert when it turns slow: the median response of the probes in scope stays above a threshold (50 to 60,000 ms) for two rounds in a row. You pick what is measured, time to first byte (the default), server time or the full response, and which probes count: those nearest your server, those in your visitors' regions, or all of them. Slow never affects uptime, and it alerts only if you turn the alert on in the monitor's settings.
Domain expiry
Not a monitor type: the domains of your monitors are collected automatically and you get an alert 30, 14, 7 and 1 days before each expires, and once on the day. It uses no credits. For a registry that publishes no date you can enter it by hand.
Notes
Every monitor has a notes field (up to 2,000 characters) for what the person on call needs: which server, who to call, what the usual cause is. Notes appear in down, partial and reminder alerts and on the monitor page, never on status pages.
Last change: 31 October 2026.