Uptime

Uptime refers to the amount of time a computer system, server, or network has been running and available without interruption. It is usually expressed as a percentage over a specific period, such as monthly or annually, and is considered one of the most important measures of system reliability. For example, an uptime of 99.9% means the system is expected to be operational for all but about 8.7 hours in a year.
High uptime is essential for businesses that rely on digital services, as even short periods of downtime can cause financial loss, reputational damage, and decreased customer trust. Cloud providers, hosting services, and IT departments often use uptime as a key performance metric.
Advanced
Uptime is closely tied to availability metrics defined in Service Level Agreements (SLAs). Systems are monitored through tools that track server responsiveness, network connectivity, and application performance. Advanced organizations strive for "five nines" (99.999%) availability, which allows for only about 5 minutes of downtime annually.
Maintaining high uptime requires redundancy, failover systems, load balancing, and proactive monitoring. In distributed and cloud environments, uptime depends not only on hardware but also on software reliability, security protections, and disaster recovery strategies. Automation, predictive analytics, and self-healing systems are increasingly used to minimize downtime risks.
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Example
A SaaS company maintained 99.99% uptime for its platform by implementing load balancing, automated failover, and continuous monitoring. This reliability improved customer retention and became a competitive advantage in service quality.