Regex Tester

Regex Tester is a free strings & text tool that runs entirely in your browser — live match highlighting, groups, flags. No upload, no account, no limits.

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How to use Regex Tester

Open the Regex Tester tool.
Paste or type your text into the input field.
The output updates as you type — adjust the options if you need a different format.
Copy the result, or share the URL to hand the exact input to someone else.

About Regex Tester

A live regular-expression tester. As you edit the pattern, matches are highlighted inline in your test string, every match and its capture groups are listed with positions, and a running count shows how many matches were found.

All five JavaScript flags — global (g), ignore-case (i), multiline (m), dotall (s) and unicode (u) — are one-click toggles, and an optional replacement field with $1/$2 references previews the substituted result.

What people use it for

Develop and debug a regex against real sample text with instant feedback.
Inspect what each capture group matches and where.
Preview a regex find-and-replace before using it in code.
Learn regex flags by toggling them and watching the matches change.

Frequently asked questions

Which regex flags are supported?

g, i, m, s and u — toggle each independently. The engine is the browser's native JavaScript RegExp.

Can I see capture groups?

Yes. Every match lists its numbered groups ($1, $2, …) and the index where it occurred.

Is there a replace preview?

Yes — add a replacement string with $1/$2 references and the substituted output appears live.

Is it private?

Every calculation happens on this page, in your own browser. Your input is never sent to a server, never logged and never used for training — which also means the tool keeps working when you are offline.