Regex Tester – Test, Validate & Debug Online
Quickly test and debug your regular expressions with our free Regex Tester tool. Perfect for beginners and advanced developers, it lets you validate regex patterns in real time, highlight matches instantly, and understand how expressions work—making pattern building faster and easier.
How does our Regex Tester Tool work?
Our Regex Tester simplifies working with regular expressions. Enter your regex pattern and test text, and the tool highlights matches instantly. It’s great for debugging complex patterns or learning the basics. How to use: 1) Enter your regex in the pattern field. 2) Type or paste text to test. 3) The tool automatically highlights matches and shows groups. 4) Use flags (g, i, m, s, u, y) to modify behavior. Invalid patterns show instant feedback so you can learn and iterate quickly.
What are the rules of regular expressions?
Regex basics include: 1) Anchors ^ and $ match start/end of line. 2) Quantifiers *, +, ?, and {n} control repetition. 3) Character classes like [a-z] and shortcuts like \d match sets and digits. 4) Grouping and capturing with ( ). 5) Alternation using |. 6) Escaping special characters with \ (e.g., \.).
What is a regular expression?
A regular expression (regex) is a special text pattern used to describe search criteria. Think of it like advanced wildcards that help you find or transform text. Example: /.*\.txt$/ matches all lines ending with .txt.
Which type of regular expression does this tool work with?
This tool uses JavaScript regular expressions and supports standard JS syntax and flags. You can use it to test patterns for JavaScript, and often adapt them for PHP, Python, Ruby, Java, and other languages with similar regex engines.
What can I use a regular expression for?
Use regex to: validate input (e.g., emails, phone numbers), search for patterns in text (e.g., find all URLs), extract data from strings, replace or reformat text, and split text into arrays based on patterns.
Can I use this tool for learning regex?
Absolutely. The tool is designed for both beginners and advanced users. Try different patterns, toggle flags, and see results instantly to build your understanding of regex.
Does this tool support regex flags?
Yes. Supported flags include: g (global), i (case-insensitive), m (multiline), s (dotAll), u (Unicode), and y (sticky).
Is my data safe?
Yes. All processing is done in your browser. No data is sent to any server.