Regex Tester
Test regular expressions in real time, inspect every match, preview capture groups, and try replacements without leaving your browser.
Global matching is used automatically for the live results list.
Live Match Preview
8 matchesReplace Mode
Use replacement tokens like $1 or $&.
Match Results
Total matches: 8This pattern matched text without capture groups.
Common Regex Library
Load a ready-made pattern and tweak it for your use case.
How to Use
- Enter your regex pattern and toggle any flags you need, like i for case-insensitive matching or m for multiline mode.
- Paste sample text into the test string area and watch matching text highlight instantly in the preview panel.
- Review the match list to see each result, its index position, and any capture groups returned by your pattern.
- Use replace mode to try a replacement string with tokens like $1 or $& and confirm the output before using it elsewhere.
- Load a common pattern from the regex library if you want a quick starting point for email, phone, URLs, IPs, dates, or ZIP codes.
Frequently Asked Questions
What is a regex tester used for?
A regex tester helps you write and debug regular expressions by showing exactly what your pattern matches. It is useful for validating input, extracting structured text, cleaning data, and testing replacements before you ship code.
What do regex flags do?
Flags change how a pattern behaves. For example, g finds all matches, i ignores letter case, m changes how ^ and $ behave across multiple lines, s lets dots match newlines, and u improves Unicode handling.
How do capture groups work in regex?
Capture groups are parts of a pattern wrapped in parentheses. When a match is found, each group stores the text matched by that section so you can inspect it or reuse it in replacements with tokens like $1, $2, and so on.
Why is my regex returning no matches?
The most common causes are missing escape characters, the wrong flags, anchors that do not match your input, or patterns that are too strict. Start with a small sample, test incrementally, and confirm whether case sensitivity or multiline behavior matters.