# Uptime: what it is and how it works · Zorraquino
> Uptime is the time a website, server or service is available, expressed as a percentage of a given period.
URL: https://www.zorraquino.com/en/dictionary/internet/up-time.html

# Uptime

Uptime is the time during which a website, server or service is available and working, usually expressed as a percentage of a given period

What it means, how it is used and where it comes up, with its related concepts.

[The whole glossary](https://www.zorraquino.com/en/dictionary)

## What it is and how it works

It is the basic availability metric; its opposite is downtime. Hosting and cloud providers usually commit to a minimum uptime in their service level agreements (SLAs), and compliance is checked with monitoring tools that query the service at regular intervals from different locations.

Differences that look small matter: 99.9% over a year allows around 8.8 hours of unavailability, whereas 99.99% cuts that margin to under an hour. It is worth checking what counts as an outage in each contract, as scheduled maintenance is often excluded.

Also known as

Availability

Topics

[Technology and data](https://www.zorraquino.com/en/dictionary/category/tecnologia-y-datos)

## Related concepts

- [Hosting](https://www.zorraquino.com/en/dictionary/internet/hosting.html)
- [Server](https://www.zorraquino.com/en/dictionary/internet/server.html)
- [Data centre](https://www.zorraquino.com/en/dictionary/internet/datacenter.html)