What is uptime monitoring?
Updated 29 October 2026 · Læs på dansk
Uptime monitoring means a program checks your website or service from the outside at regular intervals and tells you when it stops answering, so you hear about it before your customers do.
How does it work?
The monitor behaves like a visitor. Every minute (or more often) it fetches your page, checks that the answer is the expected one (for example status code 200 and a given word on the page) and records the response time. If the page does not answer, or answers wrongly, that counts as a failure. When the failure has been seen several times in a row, there is downtime and you get an alert, usually by e-mail.
Why measure from the outside?
Your own system can rarely tell you that it is down. If the server has stopped, nothing is left to send an alert. So the check has to come from somewhere other than what you monitor. It also helps to measure from several places: then you can tell the difference between your site being down for everyone and one single measuring point having a network problem.
What can be monitored?
- Websites and web shops (HTTP/HTTPS): status code, response time and optionally a word that must be on the page.
- Mail, DNS and file transfer: that a mail server answers, that name lookups work and that SFTP/SSH is up.
- Certificates: how long an SSL/TLS certificate is still valid.
What do you get out of it?
- Faster reaction: you hear about an outage within minutes instead of when a customer calls.
- Documentation: you can see when and for how long something was down and work out uptime as a percentage (see uptime percentage).
- Fewer support requests: with a status page customers can see for themselves whether the problem is known.
How to get started
Pick the pages and services that matter most to your business, describe what a correct answer looks like, and choose who gets the alert. Read more in the guide website monitoring. Tegra Uptime is a Danish-run service where you can start for free (beta).