Guide

What is uptime monitoring?

Uptime monitoring is an automated check that requests your website or service at a fixed interval from outside your network. When the check fails, the tool alerts you, so you hear about an outage before your visitors or clients tell you.

This guide explains how checks work, what the interval means, why one location is not enough, and why a working site can look down.

How an uptime check works

1. A monitoring server, often called a probe, sends a request to your URL.
2. It waits for the answer, up to a timeout.
3. It compares the answer with what you expect, for example status 200 and a word on the page.
4. If the answer is wrong or does not arrive, the tool usually checks again before it alerts you.
5. It records the result. Over time, the results give your uptime history.

Types of checks

• HTTP(S) status. Is the status code in the expected range, such as 200? A 500 or 503 means the server has a problem.
• Keyword. Does the page contain a word that should be there? This catches a page that answers 200 but shows an error or an empty template.
• Response time. How long does the answer take? Use it to see trends. A slow site is a problem, but it is not the same as a down site.
• TLS certificate. Is the certificate valid, unexpired, trusted and issued for this hostname?

Other tools also offer ping, port, DNS or heartbeat checks. For a website, HTTP(S), keyword and certificate checks cover most outages that visitors see.

What is website monitoring?

People use "website monitoring" as a wider term. It can include uptime checks, page speed tests, real user monitoring (measuring real visitors' browsers) and synthetic monitoring. Synthetic website monitoring means scripted checks from outside, such as an uptime check or a scripted login. Uptime monitoring is the simplest form of synthetic monitoring.

Check interval and detection time

The check interval is the time between two checks. It sets how late you can learn about an outage.

• With a 5-minute interval, an outage that starts just after a successful check is seen up to 5 minutes later.
• With a 1-minute interval, the same outage is seen up to 1 minute later.
• Confirmation adds a little more time, usually seconds, because the tool checks again before it alerts you.

Shorter intervals cost more, so plans differ. For example, on 8 November 2026 UptimeRobot's free plan checked every 5 minutes, Pingdom's fastest interval was 1 minute, and Better Stack's fastest was 30 seconds (UptimeRobot, Pingdom, Better Stack).

Uptime percentages translate into downtime. Over a 30-day month, 99.9% uptime allows 43.2 minutes of downtime, and 99% allows 7.2 hours.

One location or many, and how tools confirm an outage

A check from one location tests one network path. If that path fails, the tool reports your site as down while visitors elsewhere can still reach it. This is a common cause of false alarms.

Tools reduce false alarms by checking again before they alert you. They do it in different ways:

• Re-check from another server in the same region. UptimeRobot re-checks up to 3 times from different data centres in the same region. StatusCake runs 0 to 3 confirmation tests (2 by default) from other servers in the same monitoring region (UptimeRobot, StatusCake).
• Re-check from a different location. Pingdom marks a failed test as unconfirmed and retests from a probe in a different location (Pingdom).
• Require agreement across providers. A failure must be seen by probes on different hosting providers, so one provider's network problem cannot cause an alert.

Regions matter too. If a site blocks visitors from some countries, checks from those countries fail even though the site works for its real audience. Choose regions that match the site's visitors.

Why bot protection can make a site look down

Many sites use bot protection, such as a web application firewall or a CDN challenge. Monitoring probes are bots. When the protection answers a probe with a challenge page instead of the site, a simple check sees an error and reports the site as down.

Cloudflare, for example, marks its challenge responses with the header cf-mitigated: challenge (Cloudflare docs). Pingdom, UptimeRobot, StatusCake and Better Stack all tell users to allow their probes, by IP address or User-Agent, to prevent such false alerts.

Two things help:

1. Allow the probes. Add the monitoring tool's IP addresses or User-Agent to the allow list of your firewall or bot protection.
2. Report "blocked" as its own state. A challenge page does not prove the site is down. It proves the probe was stopped. A good tool tells you that, instead of waking you for an outage that does not exist.

Uptime monitoring and SSL monitoring

You need both. An expired certificate takes a site down for visitors as surely as a crashed server. Read how to monitor SSL certificate expiry.

Checklist for agencies choosing an uptime monitoring tool

• Can you group sites by client, so every alert says whose site it is?
• How does the tool confirm an outage before it alerts you: same region, other locations or other providers?
• Can you pick check regions for each monitor?
• How does it handle bot challenges? Does it publish its probe IP addresses and User-Agent?
• Does it check the certificate's expiry, chain and hostname?
• Where do alerts go: Slack, email, other channels?
• Can technicians share the work: acknowledge, assign, snooze?
• How is the price calculated: per monitor, per seat or per client?
• What is missing that you need, such as status pages or reports?

Uptime monitoring with Pingtier

Pingtier is uptime and SSL certificate monitoring for web agencies and MSPs. Its free beta opens soon. An outage counts only when at least 2 probes on different providers confirm it. It runs 8 probes on 4 providers in Europe, the US and Asia, and each monitor picks its regions. When a bot challenge answers every probe, Pingtier shows Blocked, not Down, and gives you the probe IP addresses and the User-Agent to allow. Alerts go to Slack and email.

Free during beta. Then EUR 4 per client a month, excl. VAT.

Read more: website monitoring for agencies, outage confirmation, how Pingtier checks, SSL certificate monitoring and pricing.

FAQ

What is a good check interval? It depends on how fast you need to know. A 5-minute interval finds an outage within about 5 minutes. A 1-minute or 30-second interval finds it faster but usually costs more.

What does 99.9% uptime mean in minutes? Over a 30-day month, 99.9% uptime allows 43.2 minutes of downtime. 99% allows 7.2 hours.

Why did my monitor say the site was down when it was up? Common causes are a network problem at one check location, or a firewall or bot protection that blocked the probe. Confirmation from other locations or providers, and allowing the probes, prevent most of these alerts.

Is uptime monitoring the same as website monitoring? Uptime monitoring is one part of website monitoring. Website monitoring can also include speed tests, real user monitoring and scripted user journeys.

Do I need SSL monitoring if I have uptime monitoring? Yes, unless your uptime tool also checks certificates. An expiring certificate gives a warning weeks before it breaks the site, and SSL monitoring uses that time.