Does Google see underscores "_" and hyphens "-" as dividers ?

The answer is: Google sees hyphens as dividers in URLs and body text, and ignores underscores (underscore is not considered as a divider by Google).

Below are the tests we made:

Google Test 1 : Underscores or hyphens as dividers in URL The following URL: wagatukepo-sitynozfau-mazidipole_vukertalet.php contains 4 keywords separated by hyphens or underscores. Before we started our test we did search Google for each of these keywords: wagatukepo, sitynozfau, mazidipole and vukertalet and there were no Google results. Few days later once Google indexed our new URL we did the same search for each of these keywords.

Results: wagatukepo: 1 Google result sitynozfau: 1 Google result

mazidipole: No Google result vukertalet: No Google result

mazidipole_vukertalet: 1 Google result

Conclusion: Google sees hyphens as dividers in URLs and ignores underscores

Google Test 2 : Underscores or hyphens as dividers in Body text In wagatukepo-sitynozfau-mazidipole_vukertalet.php we did type keywords: bozaketerp-boujulanbi et vorismetapalu_terplamili As for Google test 1, we did search Google for each of these keywords: bozaketerp, boujulanbi, vorismetapalu and terplamili and there were no Google results. Few days later once Google indexed our new URL we did the same search for each of these keywords.

Results: bozaketerp: 1 Google result boujulanbi: 1 Google result

vorismetapalu: No Google result terplamili: No Google result

vorismetapalu_terplamili: 1 google result

Conclusion: Google sees hyphens as dividers in Body text and ignores underscores (underscore is not considered as a divider by Google)

Our test confirms what GoogleGuy said in WebmasterWorld:

Yah, I'd stick to hyphens, periods, or commas. Most people seem to prefer hyphens. If you use an underscore '_' character, then Google will combine the two words on either side into one word. So bla.com/kw1_kw2.html wouldn't show up by itself for kw1 or kw2. You'd have to search for kw1_kw2 as a query term to bring up that page.

Related articles and tools we have used for this test