I think you are all up to date with the Canonical URL: Google, Yahoo, Live, the jointventure versus unintentional duplicate content ;) Learn more on Matt Cutt's blog.

It's a somehow cool thing but it fits best Wordpress Blogs where URLs can get into trouble every now and then. This is my second plugin related to Wordpress URLs after the Permalink Diet, which I will update these days with a bunch of new extra features based on this very plugin.

What Does The Plugin Do?

This plugin will add Canonical URL signal tag based on your current location. It will translate index, posts, pages, authors, categories, archives, tags to their canonical URL. It also points 404s and pages to homepage and if none match it will issue a canonical_url filter to ask plugins if they want to set their own value.

It also handles paged listings and will work with both query-string based permalinks and 'nice' permalinks. If a query string is present it's converted to an array and sorted that it will generate an unique canonical url even if parameters have different orders.

Query String Magic example: both http://blog/?cat=1&paged=2 and http://blog/?paged=2&cat=1 will translate to http://blog/?cat=1&paged=2. Notice query string arguments are sorted and both revert to an unique value helping rankings.

The canonical_url Filter

This plugin issues a canonical_url filter if internal methods of locating the URL fail. Your own plugins can use this to signal their own canonical URLs where the plugin can not find them. If you create custom URLs within Wordpress with your own plugins you can use this to make them search engine friendlier.

Get the FREE Google Canonical Wordpress Plugin

This section is restricted to registered users. Please register to get the Google Canonicals free Wordpress Plugin.

Pay attention to the fact that I did not test it for blogs with ... let's say custom settings. Like pages as homepage and God knows what other peculiarities people use as Wordpress settings. Let me know how it works for you. A live demo can bee seen on this very site. View source and search for "canonical".

Showing Some Appreciation

If you like it, blog about it. Many could use this. If you find bugs let me know and I'll squash them hard.
Cheers!

And don't fear the comment form. I get quite a bunch of visits but no comments. Do I leave nothing more to say? :) ... or is my comment form broken?