Runs locally in your browser.
Interactive Regex Tester
A fast, privacy-first regex evaluation engine. Test complex patterns, inspect capturing groups, and visualize matches in real-time without sending your sensitive test strings to a backend server.
//
Welcome to HiAtoms! This is a test string to match numbers like 42, 2026, or words like Developer.
No matches found.
About this Tool
The Regex Tester is a powerful, interactive sandbox for authoring, evaluating, and debugging Regular Expressions against sample text. It provides real-time match highlighting, group capturing, and syntax validation critical for text parsing and data sanitation tasks.
How It Works
Built upon the native JavaScript `RegExp` engine, the tester dynamically compiles the user's pattern and executes `.exec()` or `.matchAll()` operations against the provided test string. Match coordinates are extracted to overlay precise highlighted spans over the source text.
How to Use
- Input your Regular Expression pattern into the top input field, excluding the delimiting slashes unless using inline flags.
- Toggle necessary flags such as `g` (Global), `i` (Case-Insensitive), or `m` (Multiline).
- Type or paste test strings into the main editor to observe real-time highlighted matches and captured group arrays.
Examples
Email Validation
Matches standard email address structures.
^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$Extracting UUIDs
Identifies standard Version 4 UUID formats.
[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}Technical Notes
- FINANCIAL DISCLAIMER: This calculator provides structural estimates based on user-provided assumptions and broad, jurisdiction-level tax models. It does NOT constitute professional tax, legal, or financial advice. Actual self-employment tax liability depends on your specific business structure, elected tax treatment, applicable deductions, and the relevant fiscal year. Always consult a qualified tax professional before making financial decisions.
- The tool utilizes the PCRE-like syntax supported by modern ECMAScript implementations, including advanced features like lookaheads (`(?=...)`) and named capture groups (`(?<name>...)`).
- Catastrophic backtracking scenarios may trigger browser safeguards; extremely complex patterns should be optimized.