What is an SLA (service level agreement)?

An SLA, or service level agreement, is a written commitment about the level of service a provider will deliver. For websites it is most often an uptime percentage, with a description of how it is measured and what the customer gets if it is missed.

What does an SLA usually contain?

A target such as 99.9% uptime, the window it is measured over, how downtime is defined, which events are excluded such as planned maintenance, how the customer reports a problem and the remedy, often a credit on the bill. The details decide whether the number means anything.

What is the difference between SLA, SLO and SLI?

An SLI is a measurement, for example the share of successful requests. An SLO is an internal target for that measurement. An SLA is the external promise, with consequences, and is normally set looser than the internal target so there is room for error.

Should I offer an SLA to a client?

Only if you can measure it and your hosting can deliver it. A vague promise of 99.9% without a definition invites an argument. See the uptime and SLA calculator for what each level allows.

Where Datumboard fits

Datumboard puts the signals behind this in one dashboard for your client sites and side projects. It is in early access, and you can join the list below.