When looking for a hosting company, you come across this term frequently — uptime. For those who are confused, uptime is simply the time when the web server is running, and people can access your website. Of course, it is all but logical to assume that hosting service is always available. Even though this is what all good hosting companies strive for, with technology there are always things that can go wrong. It may be a simple need to reboot the server; it may be some user’s script that generates an infinite loop, or something else. There are thousands of unexpected things that may happen, even with the very best of companies. What distinguishes a good host from others is the time they need to solve the emerged difficulty.

Most web hosting companies offer some kind of uptime guarantee which refers to the time they know themselves to be capable of keeping their servers running in a time period of one calendar month. Usually it’s 99%, 99.9% or even 99.96%. At first glance these numbers look very similar. In reality, however, what these numbers represent, makes quite a difference.

So, what does it mean if a server has an uptime of 99%? It obviously gives you a downtime of 1%. Now, if we make a small calculation, we see that 1% of 30 days is more than 7 hours. That’s 7 hours your visitors may not open your website. Quite a long time.

With 99.9% uptime your website may be down for only 0.1%, and that is just a little over 43 minutes in one month. Much better, isn’t it? Anything better than that is already very good and rarely offered. 99.96% uptime means downtime of 0.04%, or just a little over 17 minutes per month. A minute or two down every other day is not much of a problem at all.

It’s also worth noting that not all downtime instances count under uptime guarantee. If the customer causes it, like by deleting some important configuration file, it doesn’t count. Another case that does not fall under guarantee is scheduled maintenance work. Hosting provider TOS (Terms of Service) may contain other conditions when the guarantee does not apply.

It is recommended to read the terms carefully before ordering. Sometimes these terms are written in a way that eliminates any responsibility from the host. In such cases it’s better to choose another company that is willing to guarantee good service not only in words, but also in actual deeds.

What if the contractual downtime is exceeded? When that happens the customer is entitled for a refund for that particular month. It’s not enough to refund for the time of downtime only, like some hosts think to get away with. It’s the service as a whole in this given month that was not delivered as promised. It might be useful to clarify the company policy on that too with a sales person. You should really know if the advertised number is just a slogan that has become an industry norm, or a promise that the company intends to keep.