Regex Tester & Debugger
Test, debug, and validate JavaScript regular expressions in real-time with visual pattern matching, flags selection, and group breakdown.
Common Patterns:
/
/
0 Matches Found
Invalid Regular Expression syntax.
Captured Groups & Index Details:
| Match # | Full Match | Start/End Index | Captured Groups |
|---|---|---|---|
| No matches evaluated yet. | |||
What is Regular Expression (Regex) Testing?
A Regular Expression (Regex) is a powerful sequence of characters defining a search pattern. Developers use Regex across languages like JavaScript, C#, Python, and Java for data extraction, string replacement, input validation, and lexical parsing.
This interactive tester parses your pattern on-the-fly, displaying matched substrings with visual highlight overlays and extracting sub-captures so you can verify logic before adding code to production.
Regex Quick Cheat Sheet
| Syntax Symbol | Meaning & Function | Example Match |
|---|---|---|
\d / \D |
Matches any digit (0-9) / Non-digit character. | \d+ matches 1024 |
\w / \W |
Matches any word character (alphanumeric + underscore) / Non-word. | \w+ matches user_name |
[a-z] |
Character set class - matches any character within specified range. | [A-Z] matches capital letters |
+ / * / ? |
Quantifiers: 1 or more / 0 or more / 0 or 1 (optional). | a+ matches a, aa |
^ / $ |
Anchors: Start of line / End of line. | ^https matches URLs starting with https |
( ... ) |
Capturing Group - extracts matched portion into array index. | (\d{3}) captures area codes |
Frequently Asked Questions (FAQ)
This engine uses native ECMAScript (JavaScript) RegExp mechanics directly within your browser. Patterns work seamlessly for client-side JavaScript, Node.js, and modern browser scripts.
g (Global): Finds all occurrences rather than stopping after the first match.
i (Case Insensitive): Ignores capital/lowercase letter differences.
m (Multiline): Makes
s (DotAll): Allows
i (Case Insensitive): Ignores capital/lowercase letter differences.
m (Multiline): Makes
^ and $ match start/end of individual lines.s (DotAll): Allows
. to match newline characters.
No. All evaluation, highlighters, and group extractions execute completely locally inside your browser context.