related Google Operator

The related operator searches for sites that are related to the submitted URL in terms of sites' contents. The MathWorld example below shows sites that are related to mathematics.

Example: related:mathworld.wolfram.com

This operator follows the same rules as the link operator - an invalid URL will convert the related operator into a search term and this operator should not be combined with other operators or search terms.

Use this operator when you have exhausted your list of related search terms, or if you need a quick and broad scan of a site's related contents you are completely clueless about. Note that this operator may sometimes show unrelated sites.

You can use the info operator or click on the Similar link in the results list to perform the same search.

It might be interesting to note that Wikipedia will almost always be listed in the results when you use this operator.

info Google Operator

The info operator shows a site's summary and provides links to the cache, related, link, and site search, if available. Just like the cache operator, this operator requires a valid URL for it to work.

Example: info:www.google.com

As mentioned earlier, this operator is basically the cache, related, link, and site operators rolled into one and is useful as an all-in-one replacement for these operators.

cache Google Operator

Google saves "snapshots" of pages that its Googlebot has crawled. You can view these snapshots via the Cached link in the search results.

Another method is to use the cache operator. Using this operator takes you directly to the cached version of a page.

Example: cache:en.wikipedia.org/wiki/Googlebot

The cache operator follows the same rules as the link operator. It should not be used with other operators or search terms; doing so will convert the operator into a search term. Invalid URLs will also convert the cache operator into a search term.

It is always easier to access the cached version of a page via Google's search results compared to using the cache operator. However, bear in mind that with the cache operator, you (or any other potential hacker) can dig up old pages that were removed from the search results for whatever reason.

Update

Webmasters of secure sites usually do not allow Google's caching. Such sites will not show the Cached link and will not produce any results with the cache operator.

inanchor, allinanchor Google Operator

The inanchor operator

The inanchor operator searches the anchor of a link, and not the actual URL. What is an anchor of a link?

An example of a link: Google Expert Tips. The anchor of this example is the displayed text 'Google Expert Tips'. Underlying the more readable and meaningful anchor text is the actual URL of the page. The HTML code looks like:

The inanchor operator searches within the anchor text "Google Expert Tips" in this case. This operator can be used with other operators.

Example: inanchor:scholarship inanchor:form inanchor:application site:edu

See the link operator for more details.

The allinanchor operator

The allinanchor operator searches for all search terms submitted. The following example will show the same results as the above.

Example: allinanchor:scholarship form application site:edu

This operator should not be combined with other operators. Use multiple inanchor operators if you are combining with other operators.

link Google Operator

The link operator searches for HTML links to a particular page.

Example: link:ntu.edu.sg

Note that Google shows the number of hits as usual, followed by "linking to ntu.edu.sg". This indicates a correct link search.

Take care that the link submitted should be a valid URL. An invalid URL will cause the link operator to become an ordinary search term.

This operator should not be used with other operators or search terms; doing so will convert the link operator into a search term.

Compare the link operator with the site operator. The site operator shows no result for an invalid URL whereas the link operator shows results of different context depending on the validity of the URL submitted.

You can use sub-domains to narrow search results. A neat trick is to use this operator to search for backlinks to a particular page of your site. Note that the results may not be the same as those shown in Google Analytics or Google Webmaster Tools.

filetype Google Operator

The filetype operator allows you to search for pages that end with a particular file extension, i.e. restricts a search to a certain file type.

Example: filetype:xls OR filetype:doc OR filetype:pdf site:nus.edu.sg +answers

Note that from the above example, you can view PDF files with Google Docs by clicking on Quick View. Google will also convert documents into HTML for viewing. You can view a document in HTML format by clicking on the View as HTML link.

This is useful when you do not have a required document viewer installed on your computer. However, it is always better to view the documents in their original format as the HTML conversion is not perfect - some of the contents may be missing.

Almost every file extension can be searched for. FILExt has a comprehensive list of file extensions. This operator can effectively narrow your document search when used with the site and / or intitle operators. Note that using a NOT operator with the filetype search term will not produce any results.

Examples that will not show any results:
filetype:txt -inurl:txt
filetype:txt -txt

A related operator is the ext operator.

site Google Operator

One of the more useful operators, the site operator is used to restrict a search to a particular URL or domain name. It is commonly used to search within a known website.

Example: site:americanexpress.com travel

Note that Google matches the domain names from right to left instead of the usual left to right. Therefore, all URLs used with the site operator must end with a valid registered top-level domain name.

Include sub-domains to narrow the search results.

Examples:

site:home.americanexpress.com travel

site:home.americanexpress.com/home travel

Compare the difference in the number of hits between all the above examples.