Canonical URL

Canonical URL provides a simple way to utilize the new Canonical URL Standards adopted by all of the major search engines to improve recognition of duplicated URLs. This allows you to represent information in several different places without harming your search engine rank.

Installation

Canonical URL is available both as a gem and as a standard Rails plugin. To install as a gem, add this to your environment.rb:

config.gem 'mbleigh-canonical-url', :source => 'http://gems.github.com'

To install as a traditional plugin:

script/plugin install git://github.com/mbleigh/canonical-url

Usage

The plugin is very simple to use and consists of a controller method and a helper. To set a canonical URL you will first need to add it into your site's layout, like so:

<html>
  <head>
    ...
    <%= canonical_link_tag %>
    ...
  </head>
  ...
</html>

This will automatically insert a canonical URL tag into every page of your site, defaulting to the request's current URL (it will not output anything when you have not specified a canonical URL through the controller or explicitly through the link tag). Then you can set canonical URLs in the controller as follows:

class BlogController < ApplicationController
  def show
    @post = find_post # assume this is a standard blog post type record
    canonical_url blog_post_path(post.year, post.month, post.day, post.slug)
  end
end

Now no matter what the routing is that takes you to the post, the canonical URL will remain the same.