Online Regex Tester & Debugger - Real-Time JavaScript Regular Expression Matcher
Write, test, and debug regular expressions against real sample text in real time, inspect match positions, capture groups, and ECMAScript regex flags (`g`, `i`, `m`, `s`, `u`) directly in your browser.
This tool processes your input on your device.
Developer tools
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How to use it
Follow these steps in the workspace above.
- Enter your regular expression pattern and toggle flags (`g` global, `i` case-insensitive, `m` multiline).
- Paste your test string or log sample into the test editor below.
- Inspect every highlighted match, index offset, and extracted capture group in real time.
How it works
Writing regular expressions for input validation, log parsing, URL routing, or data extraction is error-prone without instant visual feedback. Our Online Regex Tester executes your pattern directly against the ECMAScript RegExp engine in your browser, highlighting every match and breaking down numbered and named capture groups as you type.
High-Utility Regex Patterns & Flags Reference
- Flags Explained: Use
g(Global) to find all matches rather than stopping after the first;ifor case-insensitive matching;mso start and end anchors match each line; ands(dotAll) so the dot matches newline characters. - Non-Capturing vs. Named Groups: Use non-capturing groups when grouping quantifiers without allocating a capture slot, or named capture groups to extract self-documenting fields.
- Linear-Time Pattern Design: Avoid nested unbounded quantifiers on user input; prefer specific character classes and bounded repetitions.
Working on URL routing or structured data? Pair this tool with our JSON Formatter and URL Encoder & Decoder.
