Regex Tester

Regular expressions (regex) are patterns that describe how to match sequences of characters in text. They are one of the most powerful and widely used tools in programming — used for form validation (checking email addresses, phone numbers, postal codes), text search and replacement, log file parsing, URL routing, and data extraction from unstructured text.

A regex pattern is composed of literal characters and metacharacters. Literal characters match themselves exactly. Metacharacters have special meanings: . matches any character, * means zero or more of the preceding element, + means one or more, ? means zero or one, ^ anchors to the start of a string, $ anchors to the end, and brackets [ ] define character classes. Flags modify the behavior of the entire pattern.

This tester runs JavaScript's built-in RegExp engine. Enter your pattern without surrounding slashes, choose flags, provide a test string, and run the match. The tool highlights all matches in the test string and lists each match with its position and any capture groups. This interactive feedback makes it easy to build and debug complex patterns.

Common workflows include writing an email validation regex and testing it against valid and invalid addresses, building a log parsing pattern to extract timestamps and severity levels, or crafting a URL pattern for an HTTP router. All regex execution runs locally in your browser using JavaScript — no data is sent to any server.