When a set of character wants to be used, they should be used in brackets: [abc]. This regex matches only one of this set of characters. ^. could be used not to match any of the set of characters. [^abc]. matches any of the characters that are not a, b, or c. It is also possible to specify a range [0-9], [a-z] .This regex matches everything in the range. Instead of using [0-9], use the d and, for [^0-9], this express, D, can be used.