Uptime
Uptime is the percentage of time the server is running normally and your website can be accessed by visitors. The opposite is downtime — the period when the server has problems and the website cannot be opened.
Uptime is usually expressed as a percentage per year, such as 99.9% or 99.99% — and almost all hosting providers list it as a guarantee on their product pages.
Simple analogy
Uptime is like employee attendance track record. An employee with uptime of 99.9% means that out of 365 working days, he is only absent for less than 9 hours throughout the year. An employee with 95% uptime means he or she is absent almost 18 full days — quite significant if that employee is a server running your online store.
Meaning of Uptime Numbers in Real Time
The percentage numbers may seem like small differences, but the impact is very different in real time. Use Uptime Calculator to calculate estimated downtime based on your hosting uptime percentage.
| Uptime | Downtime per Month | Downtime per Year |
|---|---|---|
| 99.9% | ~43 minutes | ~8.7 hours |
| 99.95% | ~21 minutes | ~4.4 hours |
| 99.99% | ~4 minutes | ~52 minutes |
| 99.999% | ~26 seconds | ~5 minutes |
| 95% | ~36 hours | ~18 days |
The minimum industry accepted standard is 99.9% uptime. Below that figure, hosting is considered not reliable enough for business websites. Premium hosting generally offers 99.95% to 99.99%.
Uptime Guarantee vs Actual Uptime
Almost all hosting lists "uptime guarantee 99.9%" on their marketing page. But there are important differences you need to understand:
Uptime guarantee: is a written promise in the SLA (Service Level Agreement) — usually accompanied by compensation in the form of hosting credits if it is not fulfilled. This is a contractual figure.
Actual uptime: is real performance that can be measured independently with monitoring tools. This figure can be very different from what was promised, especially for budget hosting.
Don't just believe uptime claims on marketing pages. Monitor your website uptime independently using uptime monitoring guide uptime monitoring service so you have actual data as proof if you need to claim compensation.
What Causes Downtime?
Downtime can be caused by a variety of factors — not all of which the hosting provider can control:
| Causes | Description |
|---|---|
| Hardware failure | Physical damage to the server, hard disk, or network components |
| Server overload | Too many websites on one shared server, or sudden traffic spikes |
| Scheduled maintenance | Server updates that require a restart — good hosting does it during quiet hours |
| DDoS Attack | Attacks that flood servers with fake traffic |
| Configuration error | Error from the server admin side or from your own website configuration |
| Datacenter disruption | Power problems, internet connection, or natural disasters at datacenter locations |
How to Monitor Your Website Uptime
Monitoring uptime independently is an important step that website owners often ignore. Without monitoring, you only know the website is down when a visitor or client reports it.
Use a monitoring service that checks your website every 1–5 minutes from various locations
Enable email or Telegram notifications so you know instantly when the website goes down
Record the downtime history as proof if you want to claim the SLA from hosting
Also monitor response time — a slow website is often the first sign before it actually goes down
View a comparison of available monitoring services in the uptime monitoring guide to choose one that suits your needs.
Uptime Relationship with Hosting Type
The type of hosting you use greatly affects uptime stability:
| Hosting Type | Uptime Characteristics |
|---|---|
| Shared Hosting | Vulnerable to being affected by other websites on the same server |
| VPS | More stable because resources are isolated, not affected by neighbors |
| Cloud Hosting Highest uptime — | if one node has a problem, traffic automatically moves to another node Dedicated Server Stable, but if the hardware fails, all downtime is concentrated at one point |
What You Need to Pay Attention to
- Read the SLA before subscribing — Make sure the hosting includes clear compensation if the uptime guarantee is not met. Some hosts offer a guarantee but make the claim procedure very difficult.
- Scheduled maintenance does not always count as downtime — Many providers exclude maintenance windows from their uptime SLA calculations. Pay attention to this clause in the terms of service.
- High uptime does not automatically mean a fast website — The server can be in "up" status but the response time is 10 seconds. Also monitor latency and TTFB, not just online/offline status.
- CDN can help maintain accessibility when the server is down — If the website uses a CDN, visitors can still see the cached version even if the main server is having problems.
FAQs
Is 100% uptime possible to achieve?
In theory, no hosting can guarantee 100% uptime in the long term — there is always the potential for maintenance, hardware failure, or unexpected events. The "100% uptime guarantee" claims that appear on some hosts need to be read more carefully — there are usually quite broad exceptions in the SLA.
How do I claim compensation if the uptime guarantee is not met?
The procedure is different for each host, but generally: collect evidence of downtime from independent monitoring tools, then submit a ticket to hosting support with that data. Compensation is usually in the form of hosting credits, not cash. Make sure you claim within the time limit specified in the SLA.
What is the minimum uptime that is reasonable for a business website?
Minimum 99.9% for information websites or company profiles. For online stores or websites that generate direct revenue, it is best to choose hosting that offers 99.95% or more — even a few minutes of downtime can mean lost transactions.
Does downtime on my own side count toward hosting uptime?
No. Hosting uptime only measures whether the server is running normally from the hosting infrastructure side. If your website cannot be accessed because of a configuration error, problematic plugin, or unfinished domain propagation, it does not count as hosting downtime.
Disclaimer: Hosting Wiki articles are prepared for educational and reference purposes. Hosting technology keeps evolving, so some technical details may change over time.