The XML Beautify allows you to easily format and pretty-print your XML. Simply paste your XML into the tool and click the Format button. The Beautify will check that your XML is well-formed and highlight any errors that it finds. You can also open a local XML file to format.

Other features include the ability to:

Select XML in a browser tab, right-click on the selected XML, and choose "Format XML" from the menu to open a new tab and format the XML you selected.
Download the formatted XML to a file.
Save the current state for your next session.
Access other tools from LinangData from the More tools menu.
Best of all, the XML Beautify is completely free to use!