A **service level agreement** (**SLA**) is a formal contract or commitment between a [[Service provider|service provider]] and a [[Customer|customer]] that defines the expected level of service, specifying measurable performance metrics, responsibilities, and remedies that apply if the agreed standards are not met. SLAs establish a shared understanding of the quality, availability, and scope of a service, providing both parties with clarity on what is being delivered and the consequences of underperformance. They are used across a wide range of contexts including [[Information technology|IT]] services, [[Cloud computing|cloud]] infrastructure, [[Telecommunications|telecommunications]], [[Outsourcing|outsourcing]] arrangements, and internal [[IT service management|IT service management]] (ITSM) operations. SLAs typically define several categories of metrics depending on the nature of the service. **Availability** or **uptime** targets specify the percentage of time a service must be operational, commonly expressed as figures such as 99.9 percent ("three nines") or 99.99 percent ("four nines") over a defined measurement period. **Response time** and **resolution time** targets, particularly relevant in ITSM contexts, specify the maximum elapsed time within which a [[Service desk|service desk]] or support team must acknowledge and resolve [[Incident management (ITSM)|incidents]] or [[Service request|service requests]], often differentiated by [[Incident priority|priority]] level. Other common metrics include [[Throughput|throughput]], [[Latency|latency]], [[Mean time to recover|mean time to recover]] (MTTR), and [[Error rate|error rate]]. SLAs also specify the conditions under which targets are measured, exclusions such as planned [[Downtime|maintenance windows]], and escalation procedures when targets are at risk of being breached. SLAs are closely related to two related agreement types within the ITIL framework. An **[[Operational level agreement|operational level agreement]]** (OLA) is an internal agreement between IT teams within the same organization that supports the delivery of an SLA to an external customer. An **[[Underpinning contract|underpinning contract]]** (UC) is a formal contract with an external [[Third-party vendor|third-party vendor]] whose services underpin the delivery of an SLA commitment. Together, these instruments form a layered governance structure that connects customer-facing commitments to the internal and external dependencies on which they rely. In cloud service contexts, major providers including [[Amazon Web Services|AWS]], [[Microsoft Azure|Azure]], and [[Google Cloud Platform|Google Cloud]] publish standardized SLAs for individual services, specifying uptime commitments and [[Service credit|service credit]] remedies for eligible customers when targets are not met. ITSM platforms such as [[ServiceNow]] and [[BMC Software|BMC Helix]] provide SLA management capabilities that automate tracking, breach detection, and escalation workflows against defined agreement terms.