How the Regex Tester Works and When to Use It
Test regular expressions against sample text. When developers use a regex tester for validation and parsing.
How it works
You enter a regular expression and optional flags (e.g. g for global, i for case-insensitive), plus a sample string. The tester runs the regex against the text and lists each match with its index and captured groups. If the pattern is invalid, it shows a clear error message. This uses the same engine as JavaScript’s RegExp, so behavior matches your runtime.
When developers use it
Developers use it when writing or debugging regex for validation (emails, phones, IDs), parsing log lines or text, search/replace rules, or route patterns. Testing against real samples helps avoid edge cases and confirms that capture groups and flags behave as expected before putting the regex into code.