Mar 6, 2009
Hyphens or Underscores? Who wins as best keyword separator in page names?
- Are hyphens better for separating keywords in your URI (Uniform Resource Indicator)?
- If so, why not separate words with an underscore?
NOTE: Many use the term URL (Universal Resource Locator), which has been deprecated. Old habits die hard. URI is the term for the portion of a Web page’s name after the domain.
Who wins as “Best Keyword Separator” is a contest SEOs and Webmasters want to know in order to optimize websites for search engines and for users. Understanding search algorithms is an ongoing game, for sure. Knowing what’s best for people (your audience) should be thrown into the ring to determine the winner.
The issue of hyphens or underscores in file names has been discussed and debated for years.
Does the hyphen, aka a “dash,” make any difference to the search engines?
Does a hyphen or an underscore make a difference to readers?
Vanessa Fox Answers Hyphens or Underscores Question
Vanessa Fox answered the following question by Leslie Youngstrom (@LeslieY on Twitter) for WebMasterRadio.fm Office Hours show on March 5, 2009:
@vanessafox Would love to hear a definitive answer on whether to use hyphens or underscores in filenames for best SEO. Research available?
The following is a truncated summary (not verbatim transcript) of Vanessa Fox’s gracious and sage answer:
If all else being equal, does Google not give extra weight for ranking for hyphens vs. urls.
What is in url does influence extra weight into the site. What is in your URL does influence the anchor text for linking. Also, a lot of people will click on links expecting to see content based on the keywords in the URL.
If someone is linking to you, when keywords are separated by hyphens, they are seen as distinct.
Underscores may be seen in a similar way. Google has said they are looking into it – that they will start looking at underscores the same as hyphens. But I doesn’t know for sure if they have implemented this.
The reason, originally, that underscores weren’t the same as hyphens is that Google was built by programmers. They thought of underscores as joining words.
Having keywords and hyphens in URLs is important from a user experience perspective. You want the highest click-through rates. If you have keywords in your URLs, you give people an indication of what they are going to see as they click through. Hyphens do a good job of separating words. Underscores are often not seen, and users wonder if it’s a space or an underscore, because links get underlined. Readers may not get the URL right. So from a usability perspective, use hyphens.
It’s the same amount of extra work to take two or three or four of the main keywords and put them in the URL. It doesn’t take extra work to put in the hyphens.
Studies have found people are more likely to click on a short URL. Go ahead and use hyphens.
Visit Vanessa Fox’s site for Office Hours podcasts. Once latest podcasts are posted, you’ll be able to listen to her answer.
Did you catch how Leslie phrased her question – “definitive answer” and “research available?”
Vanessa’s answer gave good reasoning for best practices. She provided insight about usability and what’s best for users. We all wish Google, Yahoo! and Live Search would answer DEFINITIVELY! Part of the answer may be subjective, however. I decided to see if there are any definite results or research.
Are Hyphens more Usable?
Vanessa pointed out that the majority of websites underline links in their body copy. Users are confused when they see a page name that has underscores, which show up right next to and just above the underline.
People wonder if the underline is a space.
If underscores confuse, why put them there?
POINT: Remove any aspect of confusion in your page names.
Page Name Study
I recall usability studies that show users click through to pages with keywords separated by hyphens more than underscores. It’s also been shown that people are more likely to share and link to sites with hyphens in their domain name. I didn’t find the exact studies on these points. Interestingly, an eyetracking study by Microsoft (PDF) showed the following:
People spend 24% of their gaze time looking at the URLs in the search results.
That means people are spending time looking at your page name! So, we know it matters.
Seniors – Hyphens Study
Jakob Nielsen wrote an article about usability for senior citizens in which he explains that seniors have trouble with search engines and Web forms:
We saw users thwarted because they typed hyphens in their search queries, and punished because they used hyphens or parentheses in a telephone or credit card number.
Ah… Of course! We naturally type the hyphen as a separator. We (old and young alike) don’t naturally type the underscore.
SEO Value of Hyphens
Concensus of “repeat opinion” is that hyphens have an SEO value. Why? We know hyphens are seen as word separators. We don’t know, for sure, how Google, Yahoo! and Live Search interpret underscores.
Google’s does give their recommendation for URL structure in their Help pages.
Consider using punctuation in your URLs. The URL http://www.example.com/green-dress.html is much more useful to us than http://www.example.com/greendress.html. We recommend that you use hyphens (-) instead of underscores (_) in your URLs.
Vanessa Fox wrote about best practices for image filenames on Jane and Robot. She discusses the issue in the following paragraph:
Make image filenames descriptive
If your filename includes multiple words, use hyphens to separate them (search engines tend to see a hyphen as a separator and an underscore as a joiner (so lavendar_plant would be seen as one word and lavender-plant would be seen as two).
The following is from April 2006 from Matt Cutts’ blog, Google’s chief engineer:
And speaking of putting a dash in URLs, hyphens are often better than underscores…
Hyphen-Underscore confusion elevated after July 2007 when Google announced it was reading hyphens the same as underscores. However, Matt Cutts told us a month later that it was not yet in effect.
It’s now 2009, and the discussion and confusion continue.
Recent Research about Hyphens & Underscores
The latest post with research and ongoing discussion I found was on WebProWorld from January 19, 2009 – Whish is Better for SEO – an UNDERSCORE or HYPHEN?
Read and draw your own conclusions. The WebProWorld article doesn’t show conclusive research, however.
One opinion is worth repeating:
I have seen a lot of sources conduct basic tests to try to determine which method is better (such as the test at URLs (Update)) but most of these tests are from 2007 or before. Personally, though, I tend to be conservative and if a particular method has a historical track record of being well supported, I tend to stay with it until something comes along which is demonstrable as being an improvement.
I kept thinking about Leslie’s desire for research.
Testing How Google, Yahoo! & Live Search “Think”
Search engine result pages (SERPs) help us see how search engines think. We can’t do a Vulcan Mind Meld with the search engines on how they take in information. But we can see how they spit it out. I tried to tap into Google, Yahoo! and Live Search to see how they think about hyphens and underscores.
The following shows SERPs for various forms of “insurance rates” in the Big 3 search engines:
SERPs were different for the following:
- insurance rates – no space between keywords
- insurance-rates – hyphen between keywords
- insurance_rates – underscore between keywords
- “insurance rates” – no space, in quotation marks to return exact phrase
- “insurance-rates” – hyphen, in quotation marks to see if hyphen also returned exact phrase
- “insurance_rates” – underscore, in quotation marks to see if underscore returned exact phrase
- insurance+rates – plus sign between keywords to eliminate unrelated results
Google says they are interpreting the underscore as a word separator. If they have already implemented it, their SERPs don’t show this change. Other search engines may have as well. But if the SERPs show how they think, this research shows search engines don’t think of hyphens and underscores in the same way.
- Search results for exact phrases (keywords within quotation marks) display almost the exact same results as keywords separated by hyphens.
- Search results for keywords separated by underscores are not displayed in the same way.
We know that users are equality important, or at least they should be. People understand dashes as natural word separators. Let your readers’ desires help guide your decision about using hyphens vs. underscores. Do whatever you can to improve the user experience with your site.
Take a look around. What do you see in most URIs?
I vote for hyphens as “Best Keyword Separator.”
Should you change your URI structure?
- Don’t change your page names to hyphens if you already have underscores, unless you are doing a site redesign and are already planning on doing a lot of 301 redirects. We don’t know for sure if you will see a “lift” in the search engines. Search engines will then need to recrawl and reindex the changed URLs.
- Do consider hyphens as keyword separators for new websites and future pages .
Please share your research, opinions and conclusions. The contest about hyphens vs. underscores will surely continue.