I am looking for some help on fixing my "Username match Regular Expression". I am currently using this: ^[a-zA-Z0-9]+$ This does not permit a space within the username. However, I want to allow a single space within the username but not allow multiple spaces. So John Doe - should be valid - as should John F Doe - i.e. a space between each word. but John.......Doe is invalid as it has multiple intervening spaces - shown here as dots as I cannot enter white space. Can anybody help a I am suffering from a brain freeze with regex.