Compared, row by row.
The same list of things that break, one column per tool, every reading sourced. Enterprise suites stay a category: they cover most rows with collectors, a contract and enterprise pricing.
What breaks, by tool
| What breaks | UptimeRobot | Better Stack | Pingdom | Uptime Kuma | hostnag |
|---|---|---|---|---|---|
| A host goes downwebsite, API, VPN, mail, gateway | Yes | Yes | Yes | Yes | Yes |
| A certificate expiresdays-before thresholds, daily inside the last window | Yes | Yes | Yes | Yes | Yes |
| A domain lapsesregistration expiry from RDAP | Yes | Yes | Unknown | Unknown | Yes |
| A certificate is swappedfingerprint changed, wrong host, chain not trusted | Unknown | Unknown | Unknown | Unknown | Yes |
| A DNS record driftsexpected answer missing or changed | Yes | Unknown | Unknown | Yes | Yes |
| An ISP link dropsthe public address from several locations, confirmed by a ping from inside the site | Unknown | Unknown | Unknown | Unknown | Yes |
| Mail stops being deliveredMX, SPF, DKIM, DMARC and blocklists, at the expiry cadence of your plan | No | Unknown | No | Unknown | Yes |
| Someone issues a certificate for your domainnew certificates in the transparency logs, daily | Unknown | Unknown | Unknown | Unknown | Yes |
| A scheduled job stops runningcron, backups, workers: a heartbeat that goes quiet | Yes | Yes | Unknown | Yes | Yes |
| Your nameservers or registrar changenameservers, registrar, DNSSEC, certificate issuer, DNS answers, redirect targets | Partly | Unknown | Unknown | Unknown | Yes |
Read from each vendor's public documentation on 2026-09-15. Tell us if it changed. UNKNOWN means their documentation did not say either way on the day we read it. PARTLY is covered with a limit; each tool's page carries the reading behind every lamp.
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