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About this Tool
Regular expressions (regex or regexp) are sequences of characters that define a search pattern. They're used in programming to search, match, validate, and manipulate text based on rules rather than exact strings.
Regex is supported in virtually every programming language - JavaScript, Python, Java, PHP, Rust, Go - and in text editors, databases, command-line tools, and log analyzers.
A regex tester provides a visual interface where you can write a pattern and immediately see how it matches against a test string, which is far more efficient than running code every time you want to test a change.
Regular expressions are incredibly powerful - but writing them from memory and hoping they work is a recipe for frustration. Our Regex Tester gives you an interactive environment to build, test, and debug regex patterns in real time.
Paste your test string, write your regex, and instantly see every match highlighted in context. Capture groups, flags, global matching, and replacement strings are all supported.
Whether you're validating email addresses, extracting data from logs, or just learning how regex works - this tool makes the process visual and immediate.
How to use
- Enter your regular expression pattern in the regex input field
- Set your flags if needed , g (global), i (case-insensitive), m (multiline), s (dotAll)
- Paste or type your test string in the test input area
- Matches are highlighted in real time as you type your pattern
- Check the capture groups panel to see what each group matched individually
- Use the Replace tab to test substitution patterns and see the resulting string
Benefits
- See regex matches highlighted in real time , no need to run code to test your pattern
- Capture group visualization makes complex regex much easier to understand and debug
- Support for all major regex flags: global, case-insensitive, multiline, and dotAll
- Built-in replace testing shows the result of your substitution pattern instantly
- Common pattern shortcuts help beginners get started without memorizing syntax
- Saves significant development time when building validators, parsers, or search features
FAQs
What is regex used for in programming?
Regex is used to search, validate, extract, and replace text based on patterns. Common use cases include validating email addresses, phone numbers, and URLs; parsing log files; extracting specific data from a large text; building search-and-replace features; and cleaning up user input in forms.
What regex flags are supported?
The most common flags are: g (global , find all matches, not just the first), i (case-insensitive matching), m (multiline , ^ and $ match line start/end), and s (dotAll , makes the dot . match newline characters too). You can combine flags as needed.
How do capture groups work in regex?
Capture groups are defined with parentheses in your regex pattern. They let you extract specific parts of a match. For example, the pattern (\d{4})-(\d{2})-(\d{2}) applied to '2024-01-15' creates three capture groups: '2024', '01', and '15'. Our tester shows each group's match separately.
Can beginners use a regex tester to learn?
Absolutely. A regex tester is one of the best ways to learn regex because you get immediate visual feedback. You can experiment with small patterns, see exactly what they match, and gradually build up to more complex expressions. Many people find regex much more approachable with a live tester than when working blind in code.
Can I test regex replacement patterns?
Yes. The Replace mode lets you enter both a regex pattern and a replacement string and shows you the resulting text after substitution. You can use backreferences like $1, $2 to reference captured groups in your replacement string.
Is the regex flavor used here compatible with JavaScript?
Yes, the regex engine uses JavaScript's built-in RegExp implementation, which is the same engine used in Node.js, all major browsers, and many frontend frameworks. Patterns tested here will behave the same way when used in your JavaScript or TypeScript code.