Moving web host – will this affect my Google rankings?

A student who came on an Atracks workshop about a year ago sent in the following question a couple of days ago:

I am just about to move my website from one host to a new one and am worried I might lose my rankings in Google which are currently excellent. Is there any need for me to be concerned and is there is anything I should be doing to protect my good rankings?

In theory there is no reason why moving host should affect rankings at all – though there might be a slight dip if Google happens to come in during the short time that the site is actually being moved.
However, there are some problems that can arise if you are not careful.

The main one is that moving host often coincides with a site rebuild – perhaps the site needs to install a CMS (content management system) and sometimes hosting has to be moved to accommodate its requirements. Its when the site is rebuilt that the danger often arises. Rankings are for specific pages so if you have a No 1 ranking for an internal page, call for example, http://www.mydomain.co.uk/product.html then if this page no longer exists, the ranking will be lost. The home page address may also change, from .html to .asp for example.

There are then two options. Either the new site can be configured so that the page names are left the same – this might require the use of a mod rewrite (or similar). This is the best option if it is possible.

If this is not possible, then the new pages can be uploaded and a custom error page with a link to the new home page used so that any visitor, or bot, who lands on a ‘missing’ page will find a link to the new home page. Visitors and bots will then be able to find the new pages.

When page names are changed, use Google’s Webmaster Tools to submit a new XML sitemap to let Google know of the new pages as quickly as possible. Also, use the URL removal tool to remove the old pages from Google’s index. Then monitor the web crawl diagnostics on Webmaster Tools to check that everything is going well and no broken links have been detected.

Bear in mind though that the value of any incoming links to the old pages will be lost, which of course will affect rankings. You should be alright with links to the site that do not specify a page, ie of the type http://www.mydomain.co.uk

The worst case of loss of rankings that I have seen associated with a change of host was when a lot of images failed to be transferred correctly resulting in lots of broken links. That really did scupper rankings until it was sorted out and if it hadn’t been picked up fairly quickly using Webmaster Tools (it was not obvious from a quick visit to the site), it could have had a very long term effect.