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Regex Tool

Test regular expressions against your text with match, test, replace, and split. See match indexes plus capture groups (including named groups) without sending data anywhere.

Category: Developer · URL: /tools/regex-tool.html
Notes: This is a JavaScript regex engine. If you paste a pattern from another language, some features may differ.
Privacy: runs locally in your browser. No uploads, no tracking scripts.

How to use

This tool uses the browser's JavaScript RegExp engine (ECMAScript). For "Match", you can optionally force global iteration to list all matches.

  1. Enter a Pattern (without surrounding slashes).
  2. Set Flags (like gim) and choose a Mode.
  3. Paste your text into Text.
  4. Click Run to see matches, groups, replace output, or split parts.
Keywords this page targets (natural cluster): regex tool, regex tool online, regex tester, regex checker, regex match tester, regex replace tool, regex split tool, javascript regex tester, regex flags g i m s u y, regex named groups tester, regex capture groups viewer, find all regex matches, regex validate pattern, regex test string, regex match all, regex debug tool, regex replace count, regex escape help, multiline regex tester, unicode regex tester
Secondary intents covered: Validate that a regex pattern compiles (and see the exact error), Find all matches and their start indexes in a text block, Inspect capture groups and named groups for each match, Test whether a string matches a pattern (true/false) quickly, Run a regex-based replace and verify the final output, Split text by a regex delimiter and review the resulting parts, Compare behavior under different flags (g/i/m/s/u/y), Copy results for use in code reviews, logs, or documentation

FAQ

What regex flavor does this tool use?

It uses the browser's JavaScript RegExp (ECMAScript) engine, so behavior matches JavaScript regex rules.

Does this regex tool upload my text or pattern?

No. Everything runs locally in your browser; there are no network calls from the tool.

How do I enable case-insensitive or multiline matching?

Add flags like i (case-insensitive) and m (multiline) in the Flags field.

Why do I only see one match?

Without g, JavaScript regex finds a single match; enable g or keep “iterate all matches” checked in Match mode.

How do I view capture groups and named groups?

Use parentheses (...) for groups and (?<name>...) for named groups; the tool prints group values under each match.

My pattern has backslashes—what should I type?

Type the regex as you would in JavaScript source between slashes, but without the slashes (for example \d+).

Can I count replacements?

Yes. Replace mode shows the number of matched occurrences and the final replaced text.