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Hyphens vs. Underscores – Who Wins “Best Keyword Separator?”

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.

Hyphens vs. Underscores in URI

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?

More importantly…

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.

Hyphens vs. Underscores Links

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:

Hyphens Underscore Search Test

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

Conclusion?

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.

  1. Search results for exact phrases (keywords within quotation marks) display almost the exact same results as keywords separated by hyphens.
  2. 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?

Who Won?
I vote for hyphens as “Best Keyword Separator.”

Should you change your URI structure?

  1. 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.
  2. 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.

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Category: SEO

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23 Responses

  1. This is great information: So from a usability perspective, use hyphens. That’s the law, usability. It reads better too. Thanks for taking on the simple but hard topics. You rock!

    Uber.la’s 1-2-3 Guide To Twitter: GETTING REAL with TWITTER:

  2. John, you hit the bottom line. Even if we struggle to know what’s best for the search engines, our decisions for all our content should be based on usability! You’re right! It’s the law.

    Thanks for your input!

  3. Checkout Leslie’s POLL:

    Do you use underscores or dashes in your file naming for the best SEO results? http://twtpoll.com/nhbqgm #twtpoll

  4. Skyper says:

    An interesting observation we made is that for URLs Google seems to give higher ranking to “un-seperated” keywords… We found that a URL of ‘www.insurancerates.com’ ranked higher than ‘www.insurance-rates.com’.

    Domainers usually give un-hyphened URL a higher value – is this why?

    .S.

  5. @Skyper
    Good question. Note that a hyphenated domain can have a higher rank than a non-hyphenated domain. The domain name is one of the weights for SEO. But most brands do not build their sites on hyphenated domains.

    Domain with hyphens don’t have brand appeal, and they look cheaper and less trustworthy than non-hyphenated domains. This is why they are not as highly valued by domainers.

    Your example brings up a good point, however. “www.insurancerates.com” is a real site that provides value to users, has a PR of 3 with incoming links. “www.insurance-rates.com” is a monetized site with no PR. Google’s ultimate goal is to deliver relevant content.

    If you search for insurance-rates.com in Google, they will ask, “did you mean “insurancerates.com?” Their algorithms know how to separate keywords in a domain, and they rank sites which have what they perceive as the most relevant content to the searcher’s request.

  6. From Google…

    “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.”

    Google URL Structure
    http://www.google.com/support/webmasters/bin/answer.py?answer=76329

    Personally I would never, ever, use an underscore. And these days, I’m trimming out as many hyphens as I possibly can to create the shortest Intuitive URIs.

    Hyphens have always been the preferred separator for me. Those who have used underscores over the years are probably not totally jazzed with the negative aspects of underscored URIs. They just don’t work that well from a variety of perspectives with Usability being at the top of the list.

    Twitter Tweet Titles – Twitter / Name: Tweet Snippet …:

  7. @pageoneresults Thanks for your input! I’ve been following your research about short URIs and cut the URI of this post down to two keywords as a result!

    This is also a good opportunity to remind SEOs and bloggers that page names should not include stop or filler words, e.g. and, for, the, etc. Many publishers simply rely on their CMS to create the file name.

    What I especially appreciate about your input is that you test and research, test and research. That same approach is what motivated me to research how the search engines were “spitting out” their results. SERPs for “keyword1 keyword2″ are almost exactly the same as “keyword1-keyword2″ with “keyword1_keyword2″ showing a huge discrepancy in results.

    And, thanks for another vote for “usability!”

  8. changed from underscores to hyphens i want to say the last part of 2004.

    steveplunkett: @sushimonster FB working fine here.:

  9. I really liked your post. I will have to bookmark your site and come back later.

  10. Ok, but I still wonder, what about nospace vs no-space?

  11. @SEO-Specialist
    Thanks for addressing the issue of spaces vs no space between keywords in a URI.

    File names, as we’ve seen, do have important ramifications for SEO and usability. I didn’t address operating system and Web server compatibility.

    Never, ever use spaces in file and directory names!

    Windows & Macintosh allow spaces in a file name, however, the Web is based on UNIX protocols. Web servers running UNIX or Linux don’t recognize the space. They interpret the space as a “%20″ character. This can cause broken links on some servers and in older browsers, while others will spit out URIs as follows:

    http://www.mydomain.com/hyphens underscores/

    renders as…

    http://www.mydomain.com/hyphens%20underscores/

    The %20 will also confuse the user and those who link back to your page.

    Since linking and usability are key aspects of SEO, don’t use a space.

    Good question, thanks!

  12. [...] Vanessa Fox, SEO guru and Webmaster Central creator for Google, recently addressed this in a podcast in March. One thing she says is that having hyphens is important for the user experience because they do a good job of visually separating words, which underscores are not often seen. It leaves user to wonder if there’s a space or an underscore because links get underscored. She talks about this in a podcast on March 6, 2009 which you can find on itunes – her channel is Office hours and the session is called Cannonical Tag Adoption. Her talk (and unofficial transcript) was referenced here as well: http://pixelposition.com/hyphens-underscores/. [...]

  13. Thanks for your comment about definition lists and SEO!! I enjoy reading your blog – great topics. If you’re interested, I posted a link to the video archive of the mini-conference I spoke at on my blog. We had some great speakers and even better attendance!

    Follow-up questions from SoW09:

  14. SEO-Specialist says:

    Thanks for the clarification. But I am sorry I wasn’t clear. What I meant is which do you think is better

    http://pixelposition.com/hyphens-underscores/
    or
    http://pixelposition.com/hyphensunderscores/

  15. @SEO-Specialist Separating your keywords in your URI (page name) with a hyphen is preferable. Search engines are smart enough to detect words in a continuous string of characters. They do this with domain names all the time. However, a hyphen is a word separator that signals “keyword1-keyword2.”

  16. [...] Vanessa Fox, SEO guru and Webmaster Central creator for Google, recently addressed this in a podcast in March. One thing she says is that having hyphens is important for the user experience because they do a good job of visually separating words, which underscores are not often seen. It leaves user to wonder if there’s a space or an underscore because links get underscored. She talks about this in a podcast on March 6, 2009 which you can find on itunes – her channel is Office Hours and the session is called Cannonical Tag Adoption. Her talk (and unofficial transcript) was referenced here as well: http://pixelposition.com/hyphens-underscores/. [...]

  17. SEO-Specialist AKA Rob says:

    Dana,

    Thanks for the feedback, this question always drove me crazy because I thought maybe the SE’s might prefer the no hyphen version since it would appear more natural and yet still contain the keywords. Now that I have read your opinion, it helps me be more assured in the use of hyphens.

    Don’t mean to open another can of worms, but…. what about in the domain???

    Feel free to ad me to your network.
    http://www.linkedin.com/in/searchenginerankings

  18. [...] there is debate about whether underscores in URLs affect search results, I think the evidence in favor of using hyphens in URLs is very strong. And while some SEO specialists assert that URL structure has little if any impact [...]

  19. Shane says:

    Very interesting reading. so hyphens are as good as words squashed together, very helpful when selecting a domain name in business where most of the good ones are gone. In our case Web Design.

  20. [...] Lookadoo from Pixel Position wrote a great well-researched post on Hyphens vs. Underscores, which looks at the impact on usability and [...]

  21. [...] there is debate about whether underscores in URLs affect search results, I think the evidence in favor of using hyphens in URLs is very strong. And while some SEO specialists assert that URL structure has little if any impact [...]

  22. [...] vs 를 이용해 싸움을 시키자 역시나 이미 많은 사람들이 논의를 했었다. 링크 1 링크 2 링크 3 링크 [...]