Glossary · Reliability metrics
Service level agreement
A service level agreement (SLA) is a contract between a provider and its customers that sets a measurable service level, such as 99.9% monthly uptime, and what the customer gets, usually service credits, when it is missed.
An SLA says what is measured, over which period, how, and what is left out. The usual exclusions are announced maintenance, problems on the customer’s side and events outside the provider’s control.
The remedy is usually a credit on the next invoice, scaled by how far the level was missed: for example 10% of the monthly fee below 99.9% and 25% below 99%. Customers often have to claim it themselves, before a deadline, with their own evidence.
Teams set internal objectives (SLOs) stricter than the SLA, measured with SLIs, so they get a warning before the contract is at risk.
Allowed downtime = period × (100% − SLA)
Example: An SLA of 99.9% a month allows 43 minutes and 49 seconds of downtime in an average month; 99.95% allows 21 minutes and 54 seconds.
Uptimecheck reports show uptime, downtime and incidents per monitor for this month, last month or the last 7, 30 or 90 days, against an SLA target from 99% to 99.99%, and mark the monitors below it. Download a report as CSV, or share a live client report that is emailed on the 1st of each month.
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Guides 7 min read
An SLI measures how a service behaves, an SLO is the target for that measurement and an SLA is the promise to customers. Definitions, downtime tables and how to set each one.
ReadGuides 6 min read
99.9% uptime allows 43 minutes and 49 seconds of downtime in an average month. What each level of nines allows per day, month and year, how SLAs measure uptime, how service credits work and how to choose a target.
ReadThe SLI is the measurement, such as the share of successful checks. The SLO is the internal target for it, such as 99.95%. The SLA is the promise to customers with consequences, such as 99.9% or service credits.
Your SLA to your customers usually does, even when a hosting or DNS provider caused the outage. Their SLA to you may refund part of your bill, rarely what the outage cost you.
With independent measurements from outside the provider’s network: timestamps of when the service went down and when it came back. Keep them for the whole claim period.
Set up your first monitor in under a minute, or look around the live demo first.
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