Regex Tester — Test Regular Expressions Online

Test String

Matches

What is a Regular Expression (Regex) Tester?

A Regular Expression (regex) is a sequence of characters that defines a search pattern. Regex is used to find, match, replace, and validate text in programming. This tool lets you write and test regex patterns in real time with live match highlighting.

Common Use Cases

Validating email addresses, phone numbers, and postal codes

Extracting data from logs or text files

Find and replace operations in code editors

Form validation in web applications

Parsing structured data like dates and URLs

Tips & Best Practices

💡Use the g flag for global matching (find all matches)

💡Use the i flag to make matching case-insensitive

💡Use the m flag to make ^ and $ match start/end of each line

💡Test with ^ and $ anchors to match the entire string

Frequently Asked Questions

What is a regular expression?▼

A regular expression (regex) is a pattern used to match character combinations in strings. It is supported in almost every programming language and is used for search, validation, and text manipulation.

What does the g flag do?▼

The g (global) flag finds all matches in the string instead of stopping at the first match. Without g, the regex only returns the first match.

How do I match an email address?▼

A basic email regex pattern is: ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$

Why is my regex returning no matches?▼

Common causes: missing the g flag, wrong escape sequences, character class errors, or anchors (^ $) that are too strict. Try removing anchors first to see if any partial match works.