What is a good system uptime?

A good system uptime is 99.9% or higher. That works out to no more than about 8.76 hours of downtime over a full year, or around 44 minutes per month.

For most websites and APIs, 99.9% is a realistic and respectable target. Mission-critical systems (payment infrastructure, healthcare, communications) often aim for 99.99% ("four nines", about 52 minutes per year) or even 99.999% ("five nines", around 5 minutes per year).

The trade-off: every additional nine costs significantly more in engineering effort, redundant infrastructure, and operational discipline. Know your audience before chasing numbers for their own sake.

To actually hit and prove your uptime target, you need continuous monitoring. Oh Dear tracks every monitor and gives you a clear uptime percentage per day, month, or custom period, which you can share on a public status page or export for SLA reporting.