Home › Tools › JavaScript › Regex Tester

Regex Tester

Test regular expressions and list every match with index. Free, private and instant.

About the Regex Tester

A regular expression describes a text pattern. Testing it against sample text shows every match and its position before you put it in code.

When to use it

Use it to build validation rules, extract values from logs, or fix a pattern that matches too much or too little.

Reading a pattern

Literal characters match themselves. \d matches a digit, \w a word character and \s whitespace. Quantifiers like +, * and {n} say how many times to repeat, and parentheses create groups.

Flags

The g flag finds every match instead of the first, i ignores case, m makes ^ and $ work on each line, and s lets the dot match new lines. This tester always runs globally so you can see all matches.

Common pitfalls

Greedy quantifiers such as .* match as much as possible, so use .*? to match as little as possible. Characters like . ? and ( must be escaped with a backslash to match literally. Poorly written patterns can also run slowly on long input.

Testing strategy

Try both matching and non-matching samples, include edge cases like empty strings, and keep patterns as simple as you can. For things like emails and URLs, use a real parser when accuracy matters.