How it works
Uptime is usually expressed as a percentage over a period. 99.9 percent sounds like “almost always”, yet it allows about 43 minutes of downtime in a 30-day month; 99.99 percent leaves just over 4 minutes. If you promise clients a certain availability, you need monitoring that records outages to the minute.
It is measured from the outside: a monitor requests the website at fixed intervals and evaluates the connection, the TLS handshake, the status code, the response time and, optionally, the content. A 200 status alone does not mean the page works, since a blank page or a “Fatal error” often comes back with 200.
So that every brief blip does not page someone, good monitors wait out a failure duration before alerting. Planned work goes into maintenance windows so it does not trigger false alarms.
Why it matters
Every minute of downtime costs inquiries, orders and trust, and for online stores it costs revenue directly. Longer outages waste ad spend and leave search engine crawlers hitting errors.
For agencies it is especially awkward when the client hears about the outage before you do, say from a call by one of their own customers. Common causes are expired certificates or domains, full disks, botched updates, DNS mistakes and overloaded servers.
How to prevent it
- Monitor every client website from the outside at short intervals, not just the server from the inside.
- Also check for an expected piece of text on the page so error pages served with a 200 status get caught.
- Route alerts to a channel someone actually reads, and agree on who responds and who covers for them.
- Keep an eye on certificate and domain expiry, since both cause outages that announce themselves well in advance.
- Schedule updates in maintenance windows and keep a tested backup ready so you can roll back quickly.
How DomainWarn detects it
The Website monitor requests every monitored URL every five minutes by default; the shortest interval depends on the plan. Connection errors, timeouts and 5xx responses are critical and open the incident “Website unreachable” after the configured failure duration (5 minutes by default). An unexpected status code produces “Unexpected HTTP status”, responses above the slow threshold (5 seconds by default) produce “Website responds slowly” after three runs, and a missing required text or a forbidden one on the page produces “Page content wrong”.
From the results, DomainWarn shows availability over the last 30 days. The monthly client report states availability as a percentage along with minutes of downtime and marks a stored SLA target as met or missed. During a maintenance window, checks keep running but open no incidents.
DomainWarn checks this for all your domains on a schedule and alerts you when something is missing or changes.