Why this tool stays in the browser

Try a pattern against sample text in the tab so you can debug captures without a regex SaaS. Flags stay local. This is not a substitute for your language’s regex engine quirks — verify in the runtime you ship. Diff viewer and JSON formatter help when the haystack is a document rather than a line.

Related: JSON Formatter · Diff Viewer

FAQ

Is my log sample uploaded?: No. Matching runs in the browser.
JavaScript regex or PCRE?: The page uses the browser’s JS RegExp. Re-test in Python/Go if that is the production engine.
Can it replace my linter?: No. It is an interactive tester for patterns and captures.

RegEx Tester & Builder

Build and test regular expressions instantly against sample text. Visualize matches, test groups, and validate patterns in real-time.

Regular Expression

Test String

Results

Enter a test string to see matches highlighted

Common Patterns

Pro Tips

•Use g flag to find all matches
•Test edge cases with your patterns
•Use i flag for case-insensitive matching
•Escape special chars with \

Why this tool stays in the browser

FAQ

Is my log sample uploaded?

No. Matching runs in the browser.

JavaScript regex or PCRE?

The page uses the browser’s JS RegExp. Re-test in Python/Go if that is the production engine.

Can it replace my linter?

No. It is an interactive tester for patterns and captures.