โ Frequently Asked Questions โ Regex Tester
What regex flavour does this tool use?
This tool uses JavaScript's built-in RegExp engine, which follows ECMAScript standard regex. It supports all standard features including lookaheads, named groups (?<name>), and Unicode properties. It's compatible with regex used in Node.js, browser JavaScript, and most modern environments.
What does the 'g' flag do?
The g (global) flag finds all matches in the string instead of stopping at the first one. Without g, only the first match is found. When using JavaScript's string.replace(), the g flag is required to replace all occurrences. Without it, only the first match gets replaced.
How do I match special characters like . or *?
In regex, special characters (. * + ? ^ $ { } [ ] | ( ) \) have special meaning and must be escaped with a backslash to match them literally. For example, to match a literal dot, use \. instead of . (which matches any character). In the regex input, type \. to match a period.
What are capture groups?
Capture groups are portions of a regex wrapped in parentheses ( ). When a match is found, each group captures the portion of text it matched. They appear numbered starting from 1. Named groups use (?<name>pattern) syntax. Groups are useful for extracting specific parts of matches, like dates, emails, or phone number components.