← All Tools
Regex Tester & Debugger
Flags:
Pattern & Options
Pattern
/ /
Enter a pattern above
Replace (optional)
Test String
Matches Highlighted
Enter a regex pattern to see matches

Free Online Regex Tester — Test Regular Expressions Instantly

Test, debug and validate regular expressions against any text string in real time. Matches are highlighted as you type — no button clicks, no waiting.

🔦

Live Match Highlighting

Every match is highlighted in the test string the moment you type. Colour-coded per match group so overlapping patterns are immediately clear.

🎯

Named Capture Groups

Use (?<name>...) syntax to name your groups. The Groups panel shows each capture's value, making complex patterns easy to debug.

🔄

Replace Preview

Enter a replacement string using $1, $2 or $<name> references. See the full substituted result below the match view without writing a single line of code.

📖

Built-in Cheatsheet

Forget syntax? Click Cheatsheet for an inline quick-reference of character classes, quantifiers, anchors, groups and lookarounds — without leaving the page.

Frequently Asked Questions

What regex flavour does this tester use?
▾
This tester uses JavaScript (ECMAScript) regular expressions — the same engine used in Chrome, Firefox, Node.js and all modern browsers. It supports named capture groups (?...), lookahead, lookbehind, and the Unicode flag.
What do the flags mean?
▾
g=global (find all matches, not just the first), i=case insensitive, m=multiline (^ and $ match line starts/ends), s=dot-all (. matches newlines too), u=Unicode mode for full Unicode support.
How do I see capture groups?
▾
The Groups panel below the match count shows each numbered and named capture group value from the first match. Named groups use (?...) syntax.
Can I test a replace operation?
▾
Yes — the Replace tab lets you enter a replacement string using $1, $2 or $ for group references. The preview shows the full result of applying the replacement to your test string.
Why does my regex work in code but not here?
▾
Make sure you are not wrapping the pattern in forward slashes — enter the pattern without delimiters. Select the correct flags. This tool uses JavaScript regex, which may differ slightly from Python (re module) or PCRE.
Is there a regex cheatsheet?
▾
Yes — click the Cheatsheet button in the toolbar to open a quick reference covering character classes, quantifiers, anchors, groups and lookarounds.