Regex Tester: Validate & Debug Your Regular Expressions

Our Regex Tester Tool simplifies the process of working with regular expressions. Input your regex pattern and test string, and watch as the tool highlights matches instantly. Whether you're debugging complex patterns or learning the basics, our Regex Tester Tool is designed to make your regex experience smooth and efficient.

How to use:

1. Enter your regular expression pattern in the provided field.
2. Type or paste the text you want to test against.
3. The tool will automatically highlight all matches and display match groups.
4. Use regex flags (such as g, i, m) to modify the search behavior.

Our tool also provides instant feedback on invalid patterns, making it easy to learn and experiment with regex syntax.

A regular expression (regex or regexp for short) is a special text string for describing a search pattern. You can think of regular expressions as wildcards on steroids. You are probably familiar with wildcard notations such as *.txt to find all text files in a file manager. The regex equivalent is .*\.txt$.

Regular expressions were first developed in the 1950s by mathematician Stephen Cole Kleene and have since become a standard feature in most programming languages and text processing tools.

Regular expressions are widely used in programming languages, text editors, and command-line tools to search and manipulate text. You can use regular expressions to:

• Validate input (e.g., email addresses, phone numbers, postal codes)
• Search for patterns in text (e.g., finding all URLs in a document)
• Extract specific data from strings (e.g., capturing dates or numbers)
• Replace or reformat text (e.g., changing date formats) using a tool like the text replacer
• Split text into arrays based on patterns

They are a flexible way to work with text data and can save you a lot of time and effort when working with complex patterns.

Regular expressions match various patterns in text. Here are some of the basic rules:

1. Anchors

^ and $ are used to match the start and end of a line, respectively.

2. Quantifiers

* means zero or more, + means one or more, and ? means zero or one.

3. Character classes

[abc] matches a or b or c, [a-z] matches any letter from a to z, and [^0-9] matches anything except a digit.

4. Grouping and capturing

( ) is used to group and capture matched text.

5. Alternation

| is used to match either a or b.

6. Escaping

\ is used to escape special characters like ., *, and +.

It tests JavaScript regular expressions, using your browser's own RegExp engine, so it accepts exactly the syntax and flags that engine supports: g, i, m, s, u, y, d, and v (a flag your browser does not support is hidden). Other languages share most of the basics, such as character classes, quantifiers, and groups, but differ in the details: PHP and Python have features JavaScript lacks, such as possessive quantifiers and inline flags like (?i), and the replacement syntax differs too. A pattern that works here is not guaranteed to behave the same in PHP, Python, Ruby, or Java, so check it in that language before relying on it. If you are writing regex for a JavaScript project, the JavaScript formatter can help keep your code clean alongside your patterns.

Absolutely! The tool is designed for both beginners and advanced users. Experiment with different patterns and see instant results.

Yes. Tick any of the JavaScript flags under the pattern: g (global), i (case-insensitive), m (multiline), s (dotall), u (unicode), y (sticky), d (match indices, shown beside each match and group), and v (unicode sets). u and v cannot be used together, so ticking one clears the other. g is on when the page opens, so every match is found. You can also paste a pattern written as a JavaScript literal, such as /\d+/gi: the slashes are removed and its flags are ticked for you.

All processing is done in your browser. No data is sent to any server.