ToolingO

Regex tester / JavaScript regular expression

Test a JavaScript regular expression against sample text in your browser. Shows matches, capture groups, and replace with $1 / $&. Not .NET, Vim, or grep.

How it works
  • . — any character except newline (unless s)
  • \d — digit · \w — word character · \s — whitespace
  • * zero or more · + one or more · ? optional · {n,m} count
  • (...) capture group · [abc] character set · | alternation
  • ^ start · $ end · \b word boundary
  • Replacement uses JavaScript tokens: $1 is group 1, $& is the match, $$ is a literal $.

Enter the pattern only — do not wrap it in /slashes/.

JavaScript tokens such as $1 and $& work here. Leave empty to delete matches.


        


        

          
          
        


        

          
          
          

            
          

        

      


      

        
          
          About regex testers
        
        

          
What is a regex tester?

          
A regex tester runs a regular expression against sample text and shows each match. This page uses the browser JavaScript RegExp API, lists capture groups, and can replace matches.

          
Enter the pattern without wrapping slashes. Flags are g, i, m, s, and u. This is not .NET, Vim, or grep/PCRE. POSIX classes such as [[:digit:]] are not supported.

          
Test a regular expression in code

          

            

              
JavaScript

              
new RegExp("\\w+", "g")
"hello world".match(/\w+/g)

            

            

              
Python

              
import re
re.findall(r"\w+", "hello world")
re.sub(r"(\w+)", r"[\1]", "hello world")

            

            

              
Flags

              
g  all matches
i  ignore case
m  ^ $ at line edges
s  . matches newline
u  Unicode

            

          

        

        

          
Regex tester FAQ

          

            

              
What is a regex tester?

              
A regex tester runs a regular expression against sample text and shows each match. This page also lists capture groups and can replace matches using JavaScript $1 and $& tokens.

            

            

              
Which regex flavor does this tester use?

              
JavaScript. Patterns follow the browser RegExp API, not .NET, Vim, or grep/PCRE. Enter the pattern without wrapping slashes. POSIX classes such as [[:digit:]] are not supported.

            

            

              
How do I replace with capture groups?

              
Use $1 for group 1 and $& for the whole match. $$ is a literal dollar. Leave the replacement empty to delete matches.

            

            

              
How do I test a regular expression in code?

              
In JavaScript use new RegExp(pattern, flags) or a /pattern/g literal. In Python use re.findall or re.search. grep -E uses a different flavor.