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Regex Tester

Test regular expressions with real-time matching and group extraction.

Pattern
//g
Flags:

Quick insert:

Test String
Match Details

Enter a test string to see matches

Regex Flags

g

Global - Find all matches instead of stopping at the first.

i

Case-insensitive - Ignore case when matching.

m

Multiline - ^ and $ match line boundaries.

s

Dotall - Dot (.) matches newline characters.

u

Unicode - Enable full Unicode support.

All processing happens locally in your browser. No data is sent to any server.

How Regex Tester Works in Your Browser

The ToolsForgess regex tester evaluates regular expressions against test strings in real time, displaying matches, capture groups, and match positions with visual highlighting. Enter a regex pattern, select flags, provide a test string, and see every match highlighted instantly. The engine uses the browser's native RegExp implementation to evaluate patterns — no regex patterns, test strings, or match results are transmitted to any server. The tool supports all standard regex features including character classes, quantifiers, lookaheads, lookbehinds, named groups, and backreferences. This tool is essential for developers constructing validation patterns, debugging failing regex in code, testing search-and-replace operations, and learning regex syntax through interactive experimentation.

Key Features

  • See matches highlighted in real time as you type the regex pattern. Match positions and group captures update instantly with each keystroke.
  • Display capture group contents with numbered labels. Named groups are identified by their group name for clear result interpretation.
  • Support all regex flags including global, case-insensitive, multiline, and dot-all. Toggle flags to see their impact on match behavior.
  • All regex evaluation occurs entirely within the browser using native RegExp. No patterns or test strings are transmitted to any server.

Frequently Asked Questions

Which regex flavor is supported?
The tool uses JavaScript's RegExp engine which follows the ECMAScript specification. This includes support for lookaheads, lookbehinds, named groups, Unicode property escapes, and other modern regex features.
Can I test regex with special characters?
Yes. The tool handles all regex metacharacters, escape sequences, and Unicode characters correctly. Input strings with special characters, newlines, and Unicode are matched as expected.
Does it show regex syntax errors?
Invalid regex patterns are flagged with syntax error messages indicating the position and nature of the parsing error. This helps identify unmatched parentheses, invalid quantifiers, and other syntax issues.
Is my regex pattern stored or logged?
No. All regex evaluation occurs entirely within the browser. Your patterns and test strings are not transmitted to any server.

All data processing for Regex Tester runs 100% locally in your browser using client-side JavaScript. No data is uploaded to any server.

Technical Specification

Regular Expression Testing & Pattern Matching Engine

Overview

The ToolsForges Regex Tester provides a real-time regular expression testing environment where developers can write, test, and debug regex patterns against sample text inputs with instant visual feedback. Enter a regex pattern, select flags, and input test strings to see highlighted matches, capture groups, and match positions rendered in real time as you type.

Feature Specifications

  • Real-Time Match HighlightingSee matches highlighted in the test string as you type the regex pattern, with color-coded capture groups showing exactly which portions of the input satisfy each part of the expression.
  • Capture Group DisplayView all captured groups in a structured table showing group index, matched text, and position, enabling precise verification of complex pattern extraction logic.
  • Regex Flag ControlsToggle global, case-insensitive, multiline, and dotAll flags with checkboxes, seeing how each flag modification affects match results in real time.
  • Pattern ExplanationReceive a human-readable explanation of the regex pattern structure, breaking down each token, quantifier, and assertion for educational and debugging purposes.

Architecture

The tester uses React useState for pattern, flags, and test input. The regex engine compiles the pattern using the JavaScript RegExp constructor and applies it to the test string with matchAll for global matching. Results render with highlighted spans and a capture group table.

Frequently Asked Questions

Which regex flavor does this tool use?

The tool uses the JavaScript regex engine, which supports the ECMAScript standard including ES2015+ features like named capture groups, Unicode property escapes, and lookbehind assertions.

Can I test regex patterns for Python or other languages?

The JavaScript regex syntax is similar to PCRE used by Python and many other languages. Most basic to intermediate patterns transfer directly, but advanced features may have syntax differences.

Is there a pattern length limit?

The tool handles patterns of practical length without restriction. Very long or complex patterns may experience brief compilation delays depending on the regex engine's backtracking behavior.

Is my test data stored?

No. All regex patterns, test strings, and match results are processed entirely within your browser. No pattern-matching logic or test data is transmitted to external servers.