Regex Tester

Test, debug, and evaluate regular expressions (Regex) against sample text in real time. Displays match count, highlighted text matches, capture groups (`$1`, `$2`), and supports regex flags (`g`, `i`, `m`, `s`, `u`, `y`).

Why Use This Tool?

• Pattern Validation: Test regex patterns for email validation, phone numbers, URL parsing, or data extraction before putting them into code.
• Capture Group Extraction: Inspect extracted capture groups and named capture groups (?<name>...).
• Regex Debugging: Identify match failure edge cases and catastrophic backtracking risks.

How to Use

1. Enter Regular Expression pattern (e.g. `[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}`).
2. Select Flags (`g` global, `i` case-insensitive, `m` multiline).
3. Paste sample text to view instant highlighted matches and capture group details.

Real Working Example

Input:

Regex: (\d{3})-(\d{3})-(\d{4}) | Text: Call 202-555-0143 or 800-555-0199

Output Result:

Matches Found: 2
Match 1: "202-555-0143" (Group 1: 202, Group 2: 555, Group 3: 0143)
Match 2: "800-555-0199"

Important Technical Details & Specifications

• Native JavaScript RegExp Engine: Uses browser native ECMAScript regular expression engine for 100% fidelity.
• Named Capture Group Support: Supports modern ES2018 named capture groups (?<groupName>pattern).
• Local Memory Execution: Fast local evaluation in browser memory.

Related Developer Tools

• Regex Cheatsheet: Quick reference for regex syntax.
• Find & Replace Tool: Perform regex find and replace.
• JavaScript Beautifier: Beautify JS code.