Every minute your website is down, you're losing visitors, customers and potentially revenue. Uptime is one of the most important metrics for any website owner, yet it's often overlooked until something goes wrong.
Understanding Uptime Percentages
Hosting providers advertise uptime as a percentage. Here's what those numbers mean in practice:
What Counts as Downtime?
Downtime occurs when your website is:
- Returning a 5xx server error
- Not responding to requests (server crash)
- Extremely slow (degraded performance)
- Returning incorrect content
Note: Planned maintenance windows are often excluded from SLA calculations in the fine print.
Common Causes of Downtime
- Server hardware failure — Physical server or network equipment breaks
- Traffic spikes — More visitors than the server can handle
- Hosting provider issues — Data centre outages, network problems
- Software errors — Application crashes, bad deployments
- DDoS attacks — Malicious traffic overwhelming the server
- Expired certificates or domains — Preventable administrative failures
How to Monitor Uptime
Free and paid monitoring services check your site at regular intervals and alert you immediately when it goes down:
- UptimeRobot — Free, 5-minute checks, email/SMS alerts
- Freshping — Free tier, 1-minute checks
- Better Uptime — Premium, with incident management
- Pingdom — Industry standard, detailed performance reports
What to Look for in an SLA
A hosting SLA (Service Level Agreement) specifies the uptime guarantee and what compensation you receive if they fail to meet it. Key questions:
- What is the guaranteed uptime percentage?
- How is downtime measured and calculated?
- What credit or compensation is offered for breaches?
- Are planned maintenance windows excluded?
For most websites, 99.9% uptime is acceptable. For e-commerce or business-critical applications, aim for 99.95% or higher.