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Migration: So what is this backlink thing anyway?
Written by Sam Moffatt   
Monday, 04 February 2008 14:20

Update: This is an old blog, for the latest information about migrating check out the guide on the documentation wiki at:

So if you've used the migrator or checked out 1.5 you might have seen this strange "backlink" concept floating around the place. I was asked the question today what it was and if it is important to migrating your site. The quick answer is that its not critical though its probably something that you're going to want to have, because its cool and it attempts to keep your old menu URL's around so that you can still get to stuff with the old links. Did I mention it was also cool?

So the basic idea of backlink migration is that in 1.5 somebody went and rewrote SEF so it actually looks nice. We also have a completely new way of routing a whole heap of core components as well just to throw a lot of things off. We'll add to the fun that a lot of people out there have deployed third party SEF as well because 1.0 SEF didn't quite get the friendly part as good as what it is now in 1.5, which also adds to pain.

So if 1.5 is so different how do we handle this? There are a few options available to a stock Joomla! site: Legacy routing from the Legacy plugin and Legacy SEF from the Backlink Migration plugin. This will enable a lot of backwards compatibility for most links, especially if you're using the Core SEF (about 90% of links appear to get things right). Also to use Legacy SEF you will need to have regular SEF enabled as well and used the .htaccess file as well. However not everyone is using Core SEF, so enter the other parts of the backlink migration plugin.

So what the backlink migrator does is export your old Itemid, a name, the original URL, an SEF url (generated by the 1.0 sef system from the original URL) and a new URL so that you can pipe things manually if need be. It pulls this information from your menu table, so it will attempt to find any item in your menu and migrate it using the 1.0 SEF to try and generate an SEF url. When the backlink migration plugin is active it uses all of this information to then try to match up the old information with the new information from the database. We're basically trying to do our best to provide the ability to maintain backlinks where possible, but we can't do it for everything.

So if you were wondering about backlink migration, then that is basically it. Its pretty simple but I'm hoping it will allow more people to migrate without the pain. The basic aim is to make sure links still go somewhere, not into a 404 black hole, and that search engines will gradually update with the new links (since that is what will be handed out). Eventually your old links will go away and you can switch of all of these plugins and be happy with nice shiny SEF urls :)