Underscores vs. Dashes – SEO Tip
Update 6/10/09 – Video from Matt Cutts about the underscore vs. Dashes issue.
Spaces should never be used in a URL or file names because the space character gets translated to “%20″ by the browser, and this can wreak havoc with both readability and statistics or analytics programs. The question then remains, which is better to use instead of spaces, underscores “_” or dashes “-”.
As far as Google is concerned Big_Oak consists of one word, “Big_Oak”, and Big-Oak consists of two words, “Big” and “Oak”.
The reason Google does not treat the underscore as a word separator is because Google was created by programmers who knew that programmers often wanted to search about programming. Many computer programming languages use the underscore character in such ways that CLASS is different from _CLASS.
Because of this, I always recommend using dashes instead of underscores in your filenames and URLs. Be careful not to use too many dashes in your domain name, as that could get your site flagged for other reasons. I prefer to have a domain name with no dashes, and to use dashes where appropriate in the directory and file structure.
Other things about Google to keep in mind when choosing filenames and URL structure.
- There is no difference between lower-case and upper-case:
big oak, Big Oak, BIG OAK, and biG Oak are all the same.
- The ampersand “&” is a word seperator:
Big&Oak is treated as two words.
- Singular words are not the same as plural words:
oak and oaks are treated as different words.
- Google cannot read words that are within other words:
bubble will not be seen inside of bubblegum.
As with any tip, keep in mind that it’s a combination of many factors which will ultimately decide your placement in the search engine rankings and quite often every little bit counts.
Update: A Test
I created a test page to illustrate how Google reads words.
A search for Test_travveran shows the sample page.
A search for Flibstopper Test shows the sample page. The two words are even highlighted in the URL. The word “test” appears in the page title.
A search for travveran shows no results in Google. Google did not read my made-up word from the URL or content because it only appeared in phrases with underscores.
A site search for “choosing colors” (in quotes) shows no pages because those two words do not appear together in our site, choosing_colors on the test page is treated as a single word.
A site search for “the blue pill” (in quotes) shows our test page since dashes are treated as word separators.
A site search for “bush seo” (in quotes) shows our test page since the ampersand “&” also acts as a word separator.
Even though many of the stranger examples have little relevance to SEO, it’s a good idea to understand how Google reads and understands words.