Regex Tester & Evaluator
Test, evaluate, and debug regular expressions online. Real-time regex matching and highlighting tool for developers.
Match Result
Online Regular Expression Tester and Checker
Test, check, and debug your regular expressions in real-time. This regex tester tool uses JavaScript's native regex engine to evaluate patterns against your test strings, acting as both a regular expression checker (flagging invalid syntax) and a regex analyzer that highlights every match instantly. Secure and fully client-side — your patterns and test strings never leave the browser.
How to Use It
Type a regular expression pattern and a test string, toggle the g (global), i (ignore case), and m (multiline) flags as needed, and matches are highlighted live as you type — no need to click a separate "run" button.
Example
Pattern \d+ against the string "Order 42, Item 7" highlights "42" and "7" as matches, since \d+ matches one or more consecutive digits.
Common Use Cases
- Debugging a regex pattern before using it in production code.
- Validating that a pattern correctly matches or excludes sample strings.
- Using it as a regular expression finder to see exactly which substrings a pattern captures.
- Checking a pattern's behavior online before porting it into Java, Python, or another language.
FAQs
Which regex flavor does this use?
It uses standard JavaScript (ECMAScript) regular expression syntax, the same engine used natively in browsers and Node.js.
Can I check Java regex online with this tool?
This tool evaluates patterns using JavaScript's regex engine, not Java's java.util.regex. The two flavors are very close — most character classes, quantifiers, and groups behave the same — but they aren't 100% identical: named capture groups, lookbehind support, and some Unicode property escapes differ by engine and JavaScript runtime version. For patterns that must run exactly as they will in a Java application, verify edge cases (especially lookbehind and named groups) in a JVM before relying on results here.
Is this a regular expression checker or just a tester?
Both — it checks whether your pattern is valid (showing a syntax error if not) and tests it live against your sample text, highlighting every match as you type.
How do I find all matches, not just the first one?
Keep the "g" (Global) flag checked, which is on by default — the tool then acts as a regular expression finder that highlights every match in the test string, not only the first.
Does this work as an online regex analyzer for debugging patterns?
Yes — paste your pattern and sample text, toggle the g/i/m flags, and matches highlight live so you can see exactly what a regex does and does not capture before using it in code.