Boolean Searching

By Danny Sullivan, Editor
SearchEngineWatch.com
Page updated: Oct. 26, 2001

PLEASE NOTE: This page is still being updated for Netscape, The Open Directory and Yahoo -- though information about these services, where listed, may still be correct. These remaining services will be fully updated by mid-Jan. 2002.

Boolean search commands have been used by professionals for searching through traditional databases for years. Despite this, they are overkill for the average web user. The commands described on the Search Engine Math page provide the same basic functionality as Boolean commands and are also supported by all the major search services. If you are new to searching, start off learning how to search better by first reading the Search Engine Math page, rather than trying to learn Boolean commands. I'm certain you'll find it easier.

In fact, many professionals might benefit by abandoning Boolean commands when using web search engines. But since there is a comfort level in using what is already familiar, this page covers how Boolean commands are implemented at the major search services. It assumes you are already familiar with Boolean searching, although some resources that provide further help appear at the end of the page.

OR

The Boolean OR command is used in order to allow any of the specified search terms to be present on the web pages listed in results. It can also be described as a Match Any search. You use the command like this:

ireland OR eire

Search engines that support OR are shown on the Search Features Chart. For those that don't, see their advance search pages, where an option to search for any of your terms is often available.

Also be aware that some search engines perform an OR search by default, as shown in the Match Any section of the Power Searching For Anyone page. Search engine specific notes are below:

AOL Search

OR failed to work correctly at the time this page was written. For instance, a search for "ireland OR eire" failed to yield a much larger set of results that should have appeared when compared to "ireland AND eire".

Google

OR will not work to find different phrases, such as "bill clinton" OR "hillary clinton"

AND

The Boolean AND command is used in order to require that all search terms be present on the web pages listed in results. It can also be described as a Match All search. You use the command like this:

clinton AND dole

Search engines that support AND are shown on the Search Features Chart. For those that don't, using the + symbol is generally a good alternative.

Also be aware that some search engines perform an AND search by default, as shown in the Match All section of the Power Searching For Anyone page. Search engine specific notes are below:

AOL Search

When using AND, you may find a slightly different number of documents will be retrieved when compared to using the + symbol. This appears to be because AOL Search will check both its own listings and Inktomi listings when using AND but only Inktomi listings when using the + symbol.

NOT

The Boolean NOT command is used in order to require that a particular search term NOT be present on web pages listed in results. It can also be described as an Exclude search. You use the command like this:

clinton NOT dole

Search engines that support NOT are shown on the Search Features Chart. For those that don't, using the - symbol is generally a good alternative. Search engine specific notes are below:

AOL Search

When using NOT, you may find a slightly larger number of documents will be retrieved when compared to using the + symbol or no commands at all. This shouldn't happen, but it did at the time this page was written.

NEAR

The NEAR command is used in order to specify how close terms should appear to each other. You use the command like this:

moon NEAR river

Please consider whether you really need to control proximity within your searches. Most search engines will try to find the terms you indicate next to each other, or within close proximity to each other, by default. Also, all of the search engines support phrase searching through use of quotation marks. See Search Engine Math page for more information about phrase searching.

Search engines that support NEAR are shown on the Search Features Chart. Search engine specific notes are below.

AltaVista

NEAR means that terms will appear within 10 words of each other.

AOL Search

You can control the exact number of words apart by using NEAR/#. For instance, NEAR/5 would mean the terms should be five words apart. If you don't specify a number, then the terms must appear right next to each other.

Lycos

NEAR means that terms will appear within 25 words of each other. Lycos also supports an extensive range of other adjacency commands. See the site's help pages for Boolean searches for further details.

Nesting ( )

Nesting allows you to build complex queries. You nest queries using parentheses, like this:

impeachment AND (clinton OR johnson)

Search engines that expressly say that they support nesting are shown on the Search Features Chart. I have not tried to verify this information. Be aware that the major search engines may process nested queries differently than each other.

Other Notes

AltaVista

Boolean searching can only be done from the advanced search page, as listed on the Search Assistance Features page.

Excite, Google & MSN

Boolean commands must be in uppercase. That's why I show them that way on this page. If you always use uppercase, you won't have problems when going between services.

Inktomi- services (HotBot, MSN Search)

You must set the menu option on the home page or advanced search page to "Boolean phrase" when using Boolean commands.

Lycos

Lycos says it supports many Boolean commands, and I haven't verified these, because of the difficulty of determining exactly which datasets might be processed. In addition, AllTheWeb -- which powers many of the search results at Lycos -- doesn't support Boolean. This makes it unclear how Lycos itself might then do this.

More Resources

Boolean Searching on the Internet
http://library.albany.edu/internet/boolean.html

An easy-to-read and comprehensive guide to Boolean searching on web-wide search engines.

The Internet Search-Off
Searcher, Feb. 1998
http://www.infotoday.com/searcher/feb98/story1.htm

Lots of discussion of using Boolean commands with search engines, and why you may not get the results you expect.

Search Features Chart
Designed for searchers, an at-a-glance look at common commands and features.

Search Engine Math
This teaches you the basic commands that are all most people need to improve their searches.

Power Searching For Anyone
This teaches you advanced commands to help you better control your searches.

Search Assistance Features
Several search engines offer special search assistance features that many users overlook. This page explains the ones that are particularly useful.

Search Engine Tutorials
Links to articles and web sites that offer help with using search engines.

Search Engine Reviews
Links to reviews about the major search engines, in terms of how effective they are.