Regex Tester for JavaScript Regular Expressions
Test patterns against sample text, tune flags, inspect match indexes, and copy results without sending text to a backend.
A regex tester runs a regular expression against sample text and shows matching results.
This page uses the browser JavaScript RegExp engine, so behavior follows JavaScript regex rules.
Use realistic sample text
Test against real-looking logs, URLs, IDs, or messages instead of only one perfect example.
Check edge cases
Include empty values, repeated matches, punctuation, line breaks, and mixed capitalization.
Example
Paste log text and test an email, ID, or URL pattern before moving it into code.
Assumption
Regex behavior follows browser JavaScript rules and supported flags.
Limitation
It does not emulate regex engines from Python, PCRE, Java, or databases.
Log parsing
Test patterns for timestamps, IDs, error codes, and repeated log lines.
Form validation
Check JavaScript patterns for emails, slugs, usernames, and simple inputs.
Capture groups
Confirm that groups capture the intended pieces before using match results.
Search cleanup
Find repeated words, delimiters, URLs, or structured snippets in pasted text.
Does it support flags?
Yes. Use JavaScript flags such as g, i, m, s, u, v, y, and d when supported by the browser.
Why are results different from another language?
Regex engines vary, and this tool uses JavaScript.
Can I copy matches?
Yes. The result panel can copy matched text.
Does it need a server?
No. Testing runs in your browser.
Suggested workflow
Pattern cleanup path
Clean sample lines, test a JavaScript regex, and compare before-and-after results.