When to Use a 301 Permanent Redirect

A 301 permanent redirect tells the search engines that a certain webpage they had previously crawled has now changed, and the redirect takes them seamlessly to the replacement page. 

Other types of redirect may make the page change or redirect for a user, but it is the 301 redirect that is important for the search engines to tell them that a page has permanently changed.  If done correctly 301 redirects will minimise any drops in rankings due to website changes, whereas other redirects can cause a site to drop in positions which of course can result in lost traffic.

There are a number of different reasons for needing 301 permanent redirects.  The most common one is when changing the domain name of a website, for example from www.examplesite.com to www.newexamplesite.com.  This often happens when a company rebrands and wants to have a new URL that reflects the new brand (which is not always the best idea).  It also happens when a company has been watching a domain name that they want to have, and then buys it when it becomes available.  This may occur if a competitor goes out of business or if someone had just speculated and registered the domain but then not used it and let it expire.  

Another common reason for 301 redirects is when a couple of websites are being merged together.  This scenario can be when a subsite is being merged with a parent website, or webpages from a corporate site are being merged with a website that sold certain products the company makes.  In this case there may be pages on either site that are no longer needed because they are duplicated or outdated and so these web pages need to be 301 redirected to the certain page that is chosen to represent their content.

Some website owners purchase many domain names, often to stop competitors getting them or to hold them in case they will be used in the future.  This is a common practice in real estate industry website marketing where you might purchase lots of domains with variations of your town, city or country and the words ‘real estate’, ‘property’ and others.  A 301 redirect is the best method to point all the unused domains to the main domain that the website sits on and that is used for all marketing material.

One of the last major reasons for applying 301 redirects is to address URL Canonicalization.  This is a long word that is even harder to pronounce but it often comes up when analysing websites with Google Webmaster Tools.  URL Canonicalization occurs when a website has a number of domain names that are very similar but Google treats them as being different.  This is where the words of the body of the domain name are the same but the start or extensions are different, for example:  mysite.com, http://mysite.com and www.mysite.com all relate to the same site but Google and other search engine bots could view them as being separate.  301 redirects are needed to tell the search engine bots to focus on the main domain which normally should be the one that conforms to the common structure of http://www.mysite.com.

There are other situations when a 301 permanent redirect is the best solution to not harm your website marketing efforts, but above are the most common ones.  Some might argue that the search engine bots are smart enough to see what is happening with a site, but as the 301 redirect is recommended by Google it makes sense to follow best practice and use it.