Booleans: Your best friends when searching on the Internet

March 10, 2025

Author: Yen Verhoeven, Rano Marupova, Emily Simmons, Kate Garretson

Boolean operators are words that help you narrow or broaden your search results. Although every search engine has its unique operators, there are three main operators that most search engines use: AND, OR, and NOT. Capitalize these words to tell your search engine what to do.

AND

AND  will  narrow  your search because it tells the search engine to find results that include all the keywords. 

Let's say you are researching the evolution of dogs. Your keywords are  dogs  and  evolution.

If you simply Googled "dog," your millions of results include the latest news on dogs, the Humane Society, dogs on TikTok, Petfinder, Instagram dogs, and dog products on Amazon. 

And, if you simply Googled "evolution," your millions of results include evolution definitions, Evolution Fresh (a juicing company), evolution in education, and so on.

When you enter  dogs AND evolution, it tells the search tool to give you only results that include:

both  dogs and evolution

If you Google  dogs AND evolution, you get the purple section in Fig. 1, which includes sources like the  PBS  library on the Evolution of the Dog, a  Scientific American article on how wolves became dogs, and Smithsonian Magazine's article on the origins of dogs from wolves.

Boolean operators: All info involving dogs, all info involving evolution and in the middle the info that involves both dogs and evolution — Fig. 1. All info involving dogs (purple area: dogs AND evolution) all info involving evolution

You will  not  get any results that have:

only dog or
only evolution

So, results like the latest news on dogs, dog breeds, etc. (the red slice), or definitions of evolution, the movie Evolution, etc. (the blue slice) would be excluded from your search results.

OR  will  expand  your search because it tells the search tool to give you all the results including:

 all the results with just dogs and
all the results with just evolution and
all of the results with both dogs and evolution

If you just Googled "dog," your millions of results include the latest news on dogs, dog breeds, the Humane Society, dogs on TikTok, Petfinder, Instagram dogs, and dog products on Amazon. 

And, if you just Googled "evolution," your millions of results include definitions of evolution, Evolution Fresh (a juicing company), the movie Evolution, and so on.

When you enter  dogs OR evolution, the search tool will show you both sets of results as in Fig.2:

Fig. 2 All information involving dogs. All information involving evolution. — Fig 2. All information involving dogs. All information involving evolution.

This may seem counterintuitive (since we are programmed to think the word "and" means more, which isn't true in this case). The way to remember it is:

OR means MORE

NOT

NOT  will  narrow  your search because it tells the search tool to exclude results with a certain keyword. 

For instance, if you take your millions of results for "dogs," the NOT evolution will now exclude (subtract) any results that include evolution, even if it has the word "dog."

When you enter  dogs NOT evolution, the search tool will show you only the information in the red crescent in Fig. 3:

Fig. 3. dogs NOT All information involving evolution

This can be very useful for keywords that may have two meanings to them. 