Regex Tester

Test regular expressions online with live highlighting, match groups, named captures, replace preview and a plain-English explanation. Includes ready-made patterns.

  • Free, no sign-up
  • Runs in your browser
  • Your data stays private

How to use the Regex Tester

  1. Enter a pattern and choose the flags.
  2. Type or paste the test text.
  3. Review highlighted matches, the match table, replacements and the explanation.

Why use this Regex Tester

  • Live highlightingEvery match is coloured in the text as you type.
  • Groups and named capturesEach match lists its $1, $2 and named groups.
  • Replace previewTest replacement strings such as $1 or $<name> before using them.
  • Plain-English explainEach part of the pattern is described in simple words.

Frequently asked questions

Which regex flavour does it use?

JavaScript, the engine in your browser, including lookbehind and named groups.

What do the flags mean?

g finds all matches, i ignores case, m makes ^ and $ work per line, s lets the dot match newlines and u enables Unicode.

Why is my regex slow?

Nested quantifiers like (a+)+ can backtrack badly on long text. The tool warns about this pattern.

Related tools

More Developer Tools

User Reviews

–
No ratings yet
Write a review
Your rating *

Your email is never published. Reviews are moderated, and links aren't allowed.

What users are saying

No reviews yet

Be the first to share your experience with this tool — your feedback helps others.