It features full DTD validation, but doesn't require a DTD if you only want to do well-formedness validation. It gives meaningful messages that point you a conflict with the XML to the DTD, and tell you why your XML conflicted the DTD. It can tell you if your XML is badly formed in other ways. It has two viewing modes, "Tree" mode and "Source" mode. Source mode lets you do text editing on your XML. XML Editor will tell you exactly where in your source an error exists, and the type of error, making fixing bad XML easy.
XML Editor's graphical editor is flexible and fine tuned. You can select multiple items in the editor at once, move them around to anywhere in the document by dragging, cut, copy and paste single or multiple XML elements around, use contextual menus on selected XML. Contextual menus only show the commands that apply to the selected XML, making choices and navigation of commands simpler. You can drag XML from other programs, or from the Finder as a clipping onto the window and drag clippings out of the window to anywhere else. These are some of the useful features XML Editor offers.
XML Editor offers extensive find capabilities. A source-find mode, and a tree-find mode. The source find offers standard find/replace features. The tree find offers finding of any combination of different types of tags (DOCTYPEs, PIs, empty elements, non empty, CData, comments, text, etc). You can optionally search by name, attribute name and attribute value. You can optionally search only inside the previous search results, making complex searches possible.