Regex Tester
Test a JavaScript regular expression against sample text and highlight matches.
What Is a Regular Expression?
A regular expression, often called regex, is a pattern used to search, validate and transform text. Regex is widely used in programming, data cleanup and form validation.
Common Regex Flags
The g flag searches globally, i ignores letter case and m changes how line anchors behave in multiline text.
How to Use This Regex Tester
Enter a pattern without surrounding slashes, add optional JavaScript flags and paste test text. The tool returns each match and its position.
How to Use the Regex Tester
Enter a regular expression, add sample text and run the test to see which parts of the text match. This is useful for validating patterns before using them in code, data cleanup or form validation.
Practical Example
A pattern such as \d+ applied to the text Order 482 ships in 3 days matches the numeric values 482 and 3.
Factors That Affect the Result
Regex flavor, flags, escaping rules, anchors, greedy versus lazy quantifiers and multiline input can change the match result. Test with realistic sample data before using a pattern in production.
Frequently Asked Questions
What is a regular expression?
A regular expression is a pattern used to search, validate or transform text.
Why does my regex work differently in another language?
Regex engines can support different syntax and flags, so behavior may vary between environments.
Can this tool modify text?
Use the Regex Replace Tool when you need find-and-replace behavior.