WordPress XML to WXRby Robert Schrader
The WordPress WXR format is a special file format used for backing up, importing and exporting WordPress blogs onto other servers, whereas XML is a generic file format used for all blogs, including some WordPress blogs. It's possible to use either format to transfer a WordPress blog to another server, so it isn't necessary to convert an XML file to a WXR file, or vice-versa.
Backing Up and XML
To back up your blog's contents -- something you should do on a regular basis -- you use the "Export" tab of the "Tools" pane within the WordPress Dashboard. When you choose to export you blog's content, it downloads an XML file of the blog's posts, comments and other content onto your computer's hard drive, which you can later use to restore the blog if it becomes compromised for any reason.
Exporting to WordPress
Another option within the "Export" menu is to export the blog to another installation of WordPress. In this instance, the file that downloads is a WXR file, a special type of blog file that only works with WordPress blogs. Do not select this option if you aren't certain that you'll use the file on another WordPress server, whether via the WordPress website or on a self-hosted installation of WordPress.
Whether you have exported an XML or WXR file of your WordPress blog onto your hard drive, importing the file into WordPress follows a similar process. Namely, after selecting the "Import" option from the "Tools" pane within WordPress, you choose the "WordPress" option, then browse the computer's hard drive for the file. Once its has finished uploading into your new blog, the contents of the previous blog appear within the new one exactly as they were.
If you don't feel comfortable completing the export-import process yourself, WordPress offers a "Guided Transfer" option if your blog originates on the wordpress.com server. For a flat fee, a WordPress professional transfers your wordpress.com blog onto your own server and provides you with technical support related to the transfer for two weeks after the transfer.