Regex Tester
Build and debug regular expressions with live highlighting, capture groups, replace preview and a library of ready-made patterns.
Replace
Regex cheat sheet
.- Any character except new line
\d- Digit 0-9
\D- Not a digit
\w- Word character (a-z, 0-9, _)
\W- Not a word character
\s- Whitespace
\S- Not whitespace
\b- Word boundary
*- 0 or more
+- 1 or more
?- 0 or 1 (optional)
{3}- Exactly 3
{2,}- 2 or more
{2,5}- Between 2 and 5
*?- Lazy (as few as possible)
(abc)- Capture group
(?:abc)- Non-capturing group
(?<name>abc)- Named group
[abc]- Any of a, b or c
[^abc]- Not a, b or c
[a-z]- Range
a|b- a or b
\1- Back-reference to group 1
^- Start of string / line
$- End of string / line
(?=abc)- Followed by abc
(?!abc)- Not followed by abc
(?<=abc)- Preceded by abc
(?<!abc)- Not preceded by abc
Regular expressions run in your browser — your text is never uploaded.
How to use the Regex Tester
Write a pattern
Add flags like g, i, m, s or u.
Paste test text
Matches are highlighted as you type.
Inspect groups
See every match, index and capture group.
Why use our Regex Tester?
Live highlighting
Every match is highlighted instantly.
Capture groups
Numbered and named groups in a clear table.
Replace preview
Test $1, $<name> and $& replacements.
Pattern library
Email, URL, phone, IP, date, password and more.
Cheat sheet
Quick reference for tokens and quantifiers.
Share link
Copy a link that opens your pattern and text.
Which regex flavor is used?
JavaScript (ECMAScript) regular expressions, the same engine used in browsers and Node.js. Most syntax also works in PHP, Python and Java.
What do the flags mean?
g = find all matches, i = ignore case, m = ^ and $ match at line breaks, s = dot matches new lines, u = Unicode, y = sticky.
How do I use capture groups in replace?
Use $1, $2… for numbered groups, $<name> for named groups and $& for the whole match.
Why does my regex freeze?
Some patterns cause “catastrophic backtracking”. The tester limits the number of matches and warns you when a pattern is too slow.
Is my text sent anywhere?
No. Everything runs in your browser. The share link only includes your text if you choose to share it.
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