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Regex Tester

Write a regular expression and see its matches in your text right away, with groups, positions and a replace preview.

Runs in your browser · No uploads

Flags
Matches in the text
Use $1, $2… for groups, $<name> for named groups and $& for the whole match.
As JavaScript: /…/g
Quick reference
WriteMatches
.any character except a line break
\d \w \sa digit, a word character (letter, digit, _), a space
\D \W \Sanything but those
[abc] [^abc] [a-z]one of, none of, a range
^ $start and end of the text (or of each line with m)
\ba word boundary
a* a+ a?0 or more, 1 or more, 0 or 1
a{3} a{2,5} a{2,}exactly 3, 2 to 5, 2 or more
a*? a+?as few as possible (lazy)
(abc) (?<name>abc)a group, a named group
(?:abc)a group that isn't captured
a|ba or b
(?=a) (?!a)followed by a, not followed by a
(?<=a) (?<!a)preceded by a, not preceded by a
\. \* \(a literal . * ( (escape special characters with \)

This tester uses your browser's own JavaScript engine, so it behaves exactly like regular expressions in JavaScript. Other languages (PCRE, Python, Java) differ in some details.

  • Nothing leaves your device
  • No server-imposed size limits
  • No sign-up, no watermark
  • Free

How to test a regular expression

  1. Type the pattern between the slashes and choose flags such as g (all matches) or i (ignore case).
  2. Paste the text to search. Matches are highlighted as you type.
  3. Check the groups in the table, and try a replacement such as $1 or $<name>.

Safe to experiment

Each pattern runs with a two-second time limit, so a pattern that never finishes (catastrophic backtracking, such as (a+)+$) is stopped instead of freezing the page.

Which flavour?

This is your browser's JavaScript engine, so results are exactly what JavaScript code will do. PCRE (PHP), Python and Java mostly agree but differ in details such as lookbehind support, Unicode classes and replacement syntax.

Frequently asked questions

Why does my pattern only find one match?

Turn on the g flag to find every match; without it, only the first is found.

Is my text uploaded?

No. Everything happens in your browser, and the page is blocked from uploading anything.

Guides for this tool