About this tool
Test and debug regular expressions in real time with visual match highlighting, capture group extraction, flags support, and instant regex presets.
Regex Tester
Test regular expressions with real-time match highlighting, regex flags, capture groups, and common presets.
Optional flags: g i m s u y
Example
- preset: custom
- pattern: [A-Z]{2,}
- flags: g
- sample: LilUtils ships FAST tools.
Output
DEVWaiting
Run the tool to generate output.
When to use this tool
Use Regex Tester when writing search, replacement, or validation logic for web applications, form validation, data extraction, or log parsing.
Inputs, Formats & Specifications
- Accepted Inputs
- Regex pattern, flag selectors (`g`, `i`, `m`, `s`, `u`), sample test string
- Output Formats
- Live highlighted match preview, match count, captured groups table, execution status
- Supported Standards
- ECMAScript (JavaScript) Regular Expressions
- Browser Limits & Scope
- Conforms to modern ECMAScript RegExp standards. Specialized PCRE-only constructs (such as recursive subpatterns `(?R)`) are not supported in standard JavaScript engines.
How to use this tool
- Type or choose your regular expression pattern in the pattern input.
- Select active regex flags: `g` (global), `i` (case-insensitive), `m` (multiline), `s` (dot-all), `u` (unicode).
- Paste your test string into the text input area.
- View highlighted matches in real time along with match counts, match index ranges, and captured group values.
Examples
Email Address Validation
Test a robust email validation pattern like `^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$` against valid and invalid email test cases.
URL & Domain Extraction
Extract domain names and query parameters from server logs using named capturing groups `https?://(?<domain>[^/]+)(?<path>/[^?]*)?`.