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Regex Tester
Regex Tester
What is this tool?
A free, browser-based regex testing tool. Enter a regular expression pattern and some sample text — like a list of emails, phone numbers, or log lines — and the tool highlights every match live as you refine your pattern.
When to use it
- Validating an email address pattern before adding it to a form
- Building a pattern to match phone numbers in different formats
- Debugging why a regex isn't matching the text you expect
- Testing a pattern used for search-and-replace in code or text
- Learning regex syntax by experimenting with live feedback
How to use it
- 1Open the Regex Tester tool.
- 2Enter your regular expression pattern, including any flags you need.
- 3Paste or type sample text into the input box.
- 4Review the highlighted matches shown live in the text.
- 5Adjust your pattern until it matches exactly what you intend.
Frequently asked questions
Does this tool use JavaScript regex syntax or another flavor like PCRE?
It uses JavaScript's built-in regular expression engine, so syntax follows JavaScript regex rules and flags.
Is my sample text uploaded anywhere when I test a pattern?
No, matching happens entirely in your browser, so your text and pattern stay local.
Can I test patterns with flags like case-insensitive or global matching?
Yes, standard JavaScript regex flags are supported.
Will this tool fix my regex pattern for me?
No, it shows you what your pattern matches so you can refine it yourself; it does not auto-correct or suggest patterns.
Is there a limit on how much sample text I can test against?
There's no fixed limit, but very large text blocks may process more slowly since everything runs in your browser.