Quick definition
Website uptime is the percentage of time a website is available and accessible to users without interruption. It measures overall reliability — how often a site is "up" and serving valid responses compared with the total time monitored.
Understanding uptime percentages
Uptime is expressed as a percentage over a period (day, week, month, or year). Here's what common figures mean in practice:
| Uptime | Downtime / year | Downtime / month | Rating |
|---|---|---|---|
| 99.999% (five nines) | ~5.26 minutes | ~26 seconds | Excellent |
| 99.99% (four nines) | ~52.6 minutes | ~4.38 minutes | Very good |
| 99.9% (three nines) | ~8.77 hours | ~43.8 minutes | Good |
| 99.0% | ~3.65 days | ~7.31 hours | Average |
| 95.0% | ~18.26 days | ~36.5 hours | Poor |
Why uptime matters
Revenue loss
Every minute of downtime means lost sales, conversions, and customer opportunities — especially for e-commerce.
User trust
Frequent downtime erodes confidence. Visitors may abandon a site and turn to competitors if it is unreliable.
SEO impact
Search engines factor in availability. Repeated downtime can hurt crawl efficiency and rankings.
How we measure it
TheSiteStatus tracks uptime across multiple time windows — 30 days, 3 months, 6 months, and 12 months — and folds it into a single reliability score. The "nines" are weighted non-linearly, so the jump from 99.0% to 99.9% counts for far more than a raw 0.9% difference suggests. See exactly how on our methodology page.
What actually counts as downtime
"Down" is rarely as clean as it sounds. A site that returns a 500 error is down even though the server answered. A page that loads after 40 seconds is, for most people, down too — they gave up long before it finished. And a service can be perfectly healthy in one country while completely unreachable in another because of a DNS, CDN, or routing problem.
That's why a raw uptime percentage on its own can be misleading. We treat a check as a failure when the site doesn't return a valid, successful response within a reasonable window — not just when the connection is refused outright. It's a stricter bar, and it matches what a real visitor experiences.
Why one number can fool you
Averages hide a lot. A service that is rock-solid for eleven months and then suffers one ugly six-hour outage can still post a yearly figure north of 99.9%. The headline looks excellent; the day it fell over may have cost someone a launch, a sale, or a deadline. Two sites can share an identical uptime percentage and feel nothing alike to use — one drips a few seconds of trouble here and there, the other goes fully dark once a quarter.
This is why we keep the history visible instead of collapsing everything into a single badge. Looking at uptime month by month, next to the actual incidents behind it, tells you something a percentage never will: not just how much a site was down, but when, for how long, and whether the trend is getting better or worse.
A sensible way to read an uptime figure
- Check the window. "99.9% this month" and "99.9% over the year" are very different claims.
- Look for the incidents behind the number. One long outage and a hundred tiny blips can produce the same percentage.
- Watch the direction of travel. A site sliding from 99.95% to 99.5% is worth more attention than one sitting steadily at 99.5%.
- Remember scheduled maintenance still counts to your visitors. Planned or not, the page was unavailable.
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