When you create an Article or a Menu Item with Joomla there is a little text box for the Alias next the the text box for the title. This Alias will be what shows up in the URL for the page that is being displayed in the browser if you have the Search Engine Friendly URLs setting set to "On" in Global Configuration. If this is set to "Off" then the URLs may be some PHP generated code using the ID number for the page.

Joomla will generate an Alias upon saving the Article or Menu Item if you leave the text box blank. Joomla will simply take the title of the Article or Menu Item, make it all lowercase and pt hyphens between the words. You may choose to put in your own Alias if the title is too long or not descriptive enough. 

SEO and Joomla Aliases

To have your site be more friendly to search engines such as Google and Bing, it is best to have human readable and logical URLs for each page. The URL should be a good representation of what the content is for that page, therefore your Alias should be a good, but short, representation of the page's content.

Be careful when using Save as a Copy

If you want to copy the style of an Article so the new article has the same look and feel, or you like the unique settings that you assigned to a Category Blog or Category List, you may find yourself just opening up an existing Article or Menu Item and doing a Save as a Copy. You find yourself just erasing the copied title and putting in a new title. BE SURE TO REMOVE THE OLD ALIAS. Joomla will by default just add a number to the end of the title and to the end of the corresponding Alias. You might erase the title, but you need to be sure to erase the old alias as well. What will happen if you fail to remove the old Alias is that your new web page will have an Alias and therefore a URL that does not represent the current content on the page.

Category Lists and Category Blogs and the Article's Alias

If the Article is being displayed on your site as an Article under a Category List or Category Blog menu item, the URL for the Category Blog page or Category List page will have the Alias that you assigned when you created the Category in Category Manager. When you go to the individual article from the Blog page or List page, the URL for the individual Article will have the Alias for the Category followed by a forward slash then the id number for the Article, a hyphen, then the Alias for the Article. If the Article is accessed from a Menu Item type of Single Article, the ID for the Article will not be displayed in the URL.

Do not change the Alias on existing Articles, Categories or Menu Items unless absolutely necessary

The search engines have likely indexed your site and if you change the Alias for a previously existing Article, a Category or Menu Item, you are changing the URL for that page. This means that the URL that Google previously indexed will be wrong, resulting in a broken link for the visitor. You can alleviate this with a Redirect in your .htaccess file, but this task is often overlooked.

It is not only the Search Engines that you have to keep in mind with altered URLs. People may have bookmarked the old URL or other sites might have incoming links to the old URL.