Regular Expressions 101

^start of line

Group 1(\s*)

\s*any whitespace character, repeated any number of times

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

^(\s*)

New

<!DOCTYPE html>
<html>
  <head></head>
  <body>
    <h1>My Site</h1>
    <div id="block1">
      <p>Hello, friend!</p>
      <p>Read it:</p>
      <ul>
        <li>Item 1</li>
        <li>Item 2</li>
        <li>Item 3</li>
      </ul>
    </div>
  </body>
</html>