In web hosting uptime refers to the accessibility, availability of a server. Usually it is given in percentages. Web hosting companies generally have uptime guarantees in which they determine and promise the uptime rate that they are able to secure for users.
Uptime Guarantees Challenged
While uptime guarantees are a great thing, in most cases they are just a marketing tool in my experience. I’ve came across web hosts that claimed to provide 100% uptime of course with an extra fee, yet they were nowhere close that promise.
Other web hosts generally have 99.9% or 99.99% uptime guarantees. According to my testing web hosts promising 99.99% uptime usually have around 99.97% uptime. Weaker ones have even 99.94% on average. By the way, I pull these numbers from the 11 web hosts statistics which I monitor constantly.
So I would say that 99.97% is the uptime rate which is the most probable value.
A web host will not give your money back if they cannot keep their promised uptime rates, despite the fact that they say they will for the time of the downtime.
There are two types of downtime: scheduled and unsceduled. Scheduled downtimes are the ones which are created by the web host to do maintenance work on their systems. These need to be done by every web host from time to time, it is a must.
The problem is that the guarantee only applies to the unscheduled downtimes, and these have to be confirmed by a staff member. And we all know they will not confirm it as unscheduled.
With this being said, there is no real reason to give much credit to uptime guarantees when we choose a web host, because as I said earlier, they are just a marketing element with no real backup.