Regex Tester — Test & Replace
Test regular expressions with live highlighting, find-and-replace with regex, and browse 18+ common patterns. All free, no signup, runs in your browser.
Test Regular Expression
Find & Replace with Regex
Common Regular Expression Patterns
Click any pattern to copy it to clipboard.
What is a Regular Expression?
A regular expression (regex or regexp) is a sequence of characters that defines a search pattern. Regex is used for text search, validation, data extraction, and text replacement across programming languages, text editors, and command-line tools. Learning to write and test regex patterns is an essential skill for developers, data analysts, and system administrators.
Regex Tester — Live Match Highlighting
This online regex tester evaluates your regular expression in real-time as you type. Matches are highlighted directly in the test text, so you can see exactly what your pattern captures. Supports g (global), i (case-insensitive), m (multiline), and s (dotall) flags. Named capture groups and numbered groups are displayed below the match output.
Regex Replace — Find & Replace with Patterns
Use regex find and replace to transform text based on pattern matching. Replace all occurrences at once, or use capture groups ($1, $2) to rearrange matched content. Common use cases: reformatting dates, standardizing phone numbers, cleaning up data, and transforming log files.
Common Regex Patterns Library
Need a quick regex for email validation, URL matching, phone numbers, or hex colors? Browse our library of 18+ pre-built regular expression patterns. Click any pattern to copy it to your clipboard. Each pattern includes a description and example match.
Frequently Asked Questions
What do the regex flags mean?
g (global) finds all matches instead of stopping at the first. i (case-insensitive) ignores letter case. m (multiline) makes ^ and $ match line boundaries. s (dotall) makes . match newlines too.
How do capture groups work?
Wrap part of your pattern in parentheses to create a capture group. The matched content of each group is displayed separately. In replacements, refer to groups as $1, $2, etc. Named groups use (?<name>...) syntax.
Does this tool work the same as JavaScript regex?
Yes. This tester uses JavaScript's native RegExp engine, so results match what you'd get in Node.js or browser JavaScript. Regex behavior may differ slightly in other languages like Python or Java.
Is my data sent to a server?
No. All regex testing, replacement, and pattern matching happens 100% client-side in your browser. Your text never leaves your machine.
Can I use the common patterns in my code?
Yes. All patterns in the library are standard regular expressions. Click to copy, then paste directly into your code, config files, or command-line tools.
Is this tool free?
Yes, completely free. No signup, no usage limits, no API calls. Everything runs in your browser.