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Regex Tool Online

Use this regex tool online to test patterns, list matches (with groups), run replacements, or split text. Everything runs client-side in your browser.

Category: Developer · URL: /tools/regex-tool-online.html
Flags:
Tip: You can paste /pattern/flags in the pattern box; flags will auto-sync.
Related tools: Regex Tool · Regex Checker Online · Regex Checker Java · Hash Tool Online · YAML Formatter · XML Tool · JSON Generator from Schema · XML to PDF

          

          

            Privacy: runs locally in your browser. No uploads, no tracking scripts.
          

        

      


      
    


    

      
How to use

      
Enter your pattern and input text, then choose what you want to do.
  1. Type a pattern (either \d+ or /\d+/g) and pick flags.
  2. Select an action: Test, Match, Replace, or Split.
  3. Click Run to see the result JSON (or an error if the regex is invalid).

      

        Keywords this page targets (natural cluster): regex tool online, online regex tester, regex matcher online, regex replace online, regex split online, javascript regex tool, regex flags g i m s u y, test regex online, regex match groups, regex find all matches, regex validate pattern, regex pattern checker, regex playground online, regexp tester online, regex tool for developers, regex replace count, match all regex online, named groups regex test, escape regex characters, copy regex output
      

      

        Secondary intents covered: Test whether a regex matches a string, Find all matches with indexes and capturing groups, Do a regex-based find & replace and see replacement count, Split text by a regex delimiter (optionally with a limit), Debug invalid patterns/flags and see compile errors, Compare behavior with and without the global flag, Paste /pattern/flags and run it quickly, Copy results as JSON for debugging or sharing, Run quick sanity checks before using a regex in code
      

    


    

      
FAQ

    
Does this regex tool run server-side?
No—your pattern and text are processed locally in your browser (no network calls).
What regex flavor does this use?
It uses JavaScript RegExp (same behavior you get in modern browsers and Node.js).
Can I paste /pattern/flags directly?
Yes. If you paste something like /\d+/g, the tool will parse it and sync the flag checkboxes.
Why do I only see the first match sometimes?
Without the g flag, JavaScript returns only the first match; enable g to list all matches.
How do I reference capture groups in Replace?
Use JavaScript replacement syntax like $1, $2, or $& (whole match).
What does the Split limit do?
It limits the number of parts returned by split; leave it empty for no limit.
Why is my pattern showing “Invalid RegExp”?
The pattern or flags are not valid for JavaScript; remove unsupported flags or fix escaping (e.g., use \\ inside character escapes).