This free online tool allows you to quickly replace words or characters in a string, and also supports regular expression matching. To use regular expressions, simply click on the Regex button and enter your expression. Please note that this tool is case-insensitive, which means that if you type the word "Book", it will replace all occurrences of "Book" and "book" with the destination word.
A regular expression (regex or regexp) is a sequence of characters that defines a search pattern. It can be used to find or replace text, or to extract information from text.