SEO is a complex thing based on very complex algorithms. One of the questions that is frequently asked about SEO is that does changing web hosting affect SEO. The answer to this question can be both yes and no. Google has never explicitly said that changing web hosting has any effect on your ranking. However, there are few factors that can affect SEO negatively during change of hosts.
Changing Hosting With No Downtime
If you are changing hosts then the first thing on your mind should be to minimize the downtime. Make the process as quick as possible. In fact Google itself has given a guideline on changing hosts which simply means that have a copy of the website at the new server and when every thing is ready, change the DNS servers to point to the new web host. Up to that time your website should remain available on the old web host. By following this Google guideline you can be sure that change of web hosting will not negatively affect your SEO.
Changing Web Hosting to a Different Country
Now this is a bit tricky. There are numerous reports by users that changing web hosting to a different country does affect search engine rankings. With the change of hosting to a different country comes the change of IP where your web site is hosted. Google generally favors local website in local searches. Therefore, rule of thumb is to host your website in a country where majority of your users are located.
However, this situation can be even beneficial in the cases where you are moving your web hosting to the country where your user base is. For example if your users are in UK , then changing web hosting to UK from US will have positive affect on your SEO.
However, Google treats location independent tlDs like .com, .net and .org as location neutral and such sites are generally not affected in a big way in SEO even if the web hosting changes to a different country. But it is established that SEO is affected to a certain degree for sure.