Regex tester · Guide
Common Regex Mistakes and How to Avoid Them
A handful of mistakes account for most broken regular expressions. Recognising them saves hours of confusion.
Greedy matching
By default quantifiers are greedy: they match as much as possible. A pattern like .*" can swallow far more than one quoted string. Use a lazy quantifier (.*?) or a negated class ([^"]*) to match the minimum instead.
Unescaped special characters
Characters like . ( ) [ ] + * ? have special meaning. To match them literally, escape them with a backslash. Forgetting to escape a dot is a classic source of patterns that match too much.
Forgetting flags
Without the global flag you only get the first match; without case-insensitive you miss capitalised variants. Set flags deliberately and test with the tester to confirm coverage.
Frequently asked questions
Can I use this for production work?
Yes, for inspection, formatting and quick generation. Still review the output before committing it to production code or configuration.
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