The main problem in migrating old content to new URLs is to maintain ‘age equity’ – an important trust factor that affects rankings – and to prove to Google that we didn’t simply steal the content, which would incur penalties if noticed or even suspected.
Solution: redirects
Redirect old URLs to new URLs. Don’t just scrap the old domain and waste all that hard-earned trust!
Don’t forget to update links
Updating in-content links is also important. Some kind of site-wide search & replace tool can be helpful here. Without this, you risk the common problem of links pointing to old pages or old sites – sometimes this is a test/staging environment that’s still being linked to.
Be careful & accurate
If you’re not careful in how you update in-content links, and especially if you mis-configure your redirects from your old pages to your new ones, not only can you end up creating lots of error 404s, but even worse, you could end up with infinite redirect loops which are a sign of serious neglect, often causing browsers and crawlers to over-work themselves or even crash.
Branding connotations
Where content migration is part of a rebranding exercise then you also need to be careful to update all references to the old brand, otherwise you risk looking disorganised and out-of-date, which makes your business look less professional. Obviously error pages are not a good look for your brand either!
Penalised sites – an exception to the rule
An important caveat to note when redirecting content to a new site would be if you are migrating because site A was penalised – this would be one of the rare cases where you might want to avoid redirecting to site B.
How to re-purpose the content of penalised sites
Re-purpose the content with caution, because it may have been that very content that got you penalised! Or Google may still be associating that content with your site’s penalty. Either way, be careful in re-using it.
Definitely don’t transfer your site’s equity in its entirety by means of URL redirection, because part of that equity is certainly a penalty, although this is difficult to prove because it’s treated in a complex manner (with sandboxing (delayed effects) and variation based on a number of factors) in order to avoid it being used for negative SEO (ie, by redirecting your penalised site to your competitor’s site).