You will witness an adverse effect on your rankings, web traffic, and revenues in case you fail to provide proper redirects of your important web-pages when you migrate to another platform or wish to lead visitors to newer pages. You must make a pre and post migration plan to avoid facing multiple problems during platform migration.
Before you undertake that frightening migration exercise, you must engage in pre migration moves that involve auditing your website to remove outdated pages as well as make a list of relevant and important pages. You can export that information by using the Google Webmaster Tools. You need to go to the Top Pages section after going into Search Queries. You should then click on Download Chart Data to export the required information.
This information will contain important statistics of your web pages including impressions, click-through data, and position. Additionally, you will also need to use other tools such as those offered by Majestic SEO to get information on external backlinks. You need to learn about those pages that are most popular on your website. The resultant URL list will again need to be audited to confirm if they actually exist and if they can be successfully matched with the new pages.
A 301 redirect is appropriate for several redirect situations. A direct redirection is very easy and is used to redirect to a matching old and new webpage. In case an old product page has been discontinued then you may need to use a 301 redirect to take visitors to the next best matched product page or to a sub-category of that product. Alternatively, you can redirect to the parent category or page if the entire product line is discontinued.
If there are no matching pages when an old one is put to rest then you must use the 404 no redirection option. You also need to consider redirection and migration costs, and using redirections through servers will be much more cost-effective than opting through CMS.
You must also restrict your redirects to less than 100, if possible. You will need better infrastructure to seamlessly handle more redirects. You should also try using regular expressions, wherever possible to reduce their numbers. Testing your redirections quickly will prevent ranking loss.
You must utilize 301 redirects in case of site migrations and 302 redirects for temporary redirects. You must also make a visitor-friendly 404 page to tackle redirects that may not have been successful.
Once you have implemented your migration or redirection plan, then you also need to engage in post-migration exercises to minimize any harm in case of any problem. You should quickly engage in site analytics to locate your most popular pages before your migration since you may be able to actually execute all redirects before your new website is indexed by Google.
You must anyway, expect some loss in ranking immediately after migration or redirection and achieving your earlier ranking may depend on just how competitive your niche is since higher competition levels will require a lot more effort.
In case you have migrated without a proper plan and your new site is indexed by Google then you will surely witness a dramatic drop in rankings along with a drop in traffic. In such a scenario, it may be wise to save all possible link juice by opting to complete all redirects. You may also need to seek out all dead links by viewing your backlink profile. You can then identify good websites and email them to make sure that your broken links are repaired by way of new links. You may even have to start a new link-building campaign from the ground up.
In case you have already initiated your migration or redirection exercise or plan to do so in the near future then you should pay heed to the above SEO tips to avoid damage to your rankings, traffic, and sales.