Bing offers various advanced query operators, helping bing.com customers and Bing API customers to refine their query to match their needs. Two of these operators  – filetype: and ext: – appear to be same but there are subtle differences.  Let’s review each to better understand them.

filetype:

One of the most commonly used operators is filetype: which enables you to filter documents based on their particular filetype.   Usually  this operator is used to filter search results to html, txt, and pdf, as well as the primary Office document types: doc, rtf, xls, and ppt for Word, Excel, and PowerPoint documents. This is useful for finding official forms which are usually in PDF or DOC format… for example, 1040 filetype:pdf for the official IRS 1040 for US Taxes.

ext:

ext: is used to return the webpages of the specified file name extension only. This is also helpful for finding URLs ending in specific formats… for example, template ext:docx will filter search results to URLs having extension .docx, one of the new Microsoft Office Open XML formats introduced with Microsoft Office 2007.

So what’s the difference between filetype and ext?

The key difference between these two operators is as follows.  The Bing filetype: operator is based on our classification of the content associated with URLs, and the bing ext: operator is only based on the URL file extension.   You should note that filetype: covers the high level type, not individual version. In other words, filetype: DOC, DOCX and WORD will all result in the same thing (filtering to MSDOC documents.)

Internet URLs can be ambiguous. For instance, URLs can be end with .pdf but they may not be Adobe Portable Document Format pdf files, as this example shows http://en.wikipedia.org/wiki/File:World.pdf; and the opposite is also true. URLs can end with .html and actually be a PDF file: example http://www.eia.gov/emeu/steo/pub/special/enviro.html

Also, the Bing filetype: operator is based on our classification of the content associated with URLs, and the Bing ext: operator is only based on the URL file extension. This offers Bing customers the ability to refine their queries to match their needs. For instance, the following query template filetype:doc ext:docx combines filteype and ext and will filter search results to Microsoft Word documents having the docx Office Open XML formats.

Webmasters can also use such operator to audit files indexed within their site via site:wikipedia.org filetype:pdf .