Regex Tester | Regular Expression Tester - DevToolKit
Free online regex tester. Test regular expressions against sample text with real-time match highlighting. Supports JavaScript regex syntax.
Common Regex Patterns
What is Regex Tester?
How to Use Regex Tester
Enter your regular expression in the regex input field. Toggle flags (g, i, m, s) as needed. Type or paste your test string in the text area below. Matches are highlighted in real time. The match results section shows each match with its index, captured groups, and total match count.
How Regex Tester Works
Common Use Cases
- Building and testing regex patterns for form validation
- Debugging regular expressions used in JavaScript code
- Extracting data from log files or structured text
- Learning regex syntax with instant visual feedback
- Testing patterns for search-and-replace operations
Frequently Asked Questions
What regex syntax does this tool support?▼
This tool supports JavaScript (ECMAScript) regular expression syntax, including character classes, quantifiers, groups, lookaheads, lookbehinds, and named capture groups.
What do the regex flags mean?▼
g (global) finds all matches, i (case-insensitive) ignores case, m (multiline) makes ^ and $ match line boundaries, and s (dotAll) makes . match newline characters.
Why does my regex work differently here than in Python/Java?▼
Different programming languages have slightly different regex engines. This tool uses JavaScript regex syntax. Some features like possessive quantifiers or atomic groups are not available in JavaScript.
Is my test data sent to a server?▼
No. All regex testing happens in your browser using the native JavaScript RegExp engine. No data leaves your machine.