Test regular expressions with live matching, highlighting, and capture groups. Real-time validation as you type.
Our free Regex Tester lets you write, test, and debug regular expressions with live match highlighting, capture group details, and real-time validation. See exactly what your pattern matches as you type, with color-coded highlights and detailed match information for every result.
Whether you're a developer validating form inputs, a data analyst extracting patterns from text, or a student learning regex syntax, this tool provides everything you need in one clean interface.
A regular expression (regex or regexp) is a sequence of characters that defines a search pattern. Regular expressions are used in programming, text processing, and data validation to find, match, extract, or replace text that follows a specific pattern. They are supported natively in virtually every programming language including JavaScript, Python, Java, PHP, Ruby, and many others.
Regex patterns can range from simple (matching a specific word) to highly complex (validating an email address or parsing a log file format). The power of regular expressions lies in their ability to describe patterns abstractly — for example, "a string that starts with a digit, followed by one or more letters, ending with a period" — rather than matching only a single specific string.
This tester uses JavaScript's built-in RegExp engine, which follows the ECMAScript standard. It supports all standard regex features including character classes, quantifiers, anchors, groups, backreferences, lookaheads, and lookbehinds, as well as the g, i, m, and s flags.
Always enable the "g" (global) flag when you want to find all matches in a string, not just the first one. Without the global flag, the regex engine stops after finding the first match. The match count in the stats bar will show "1" even if there are multiple matches in the text, which can be misleading when debugging.
Use capture groups (parentheses) to extract specific parts of a match. For example, the pattern (\d{4})-(\d{2})-(\d{2}) matches a date in YYYY-MM-DD format and captures the year, month, and day as separate groups. The Match Details section will show you the value of each group for every match, making it easy to verify your extraction logic.
When writing complex patterns, build them incrementally. Start with a simple pattern that matches part of what you need, verify it works, then add more specificity. Trying to write a complete complex pattern all at once and then debugging it is much harder than building it step by step. The real-time feedback in this tester makes the incremental approach fast and intuitive.
Many regex testers are cluttered with ads, require registration, or lack the detailed match information that makes debugging efficient. Our tester provides a clean, focused interface with all the information you need — match highlighting, capture groups, match positions, and flag controls — without any distractions.
The real-time highlighting is particularly valuable for visual learners and for debugging complex patterns. Seeing exactly which parts of your test string are matched (and which aren't) makes it immediately obvious whether your pattern is working as intended, without having to mentally trace through the regex logic yourself.
Since the tester runs entirely in your browser, you can use it with sensitive data — like real log files, customer data samples, or proprietary text formats — without worrying about that data being transmitted to or stored on a remote server.
Your privacy is our priority. All processing happens entirely in your browser using JavaScript. No files, data, or inputs are ever uploaded to any server. Everything stays on your device, making this tool completely safe to use with sensitive content.