Regex Tester Online | Test and Debug Patterns

What Is This Tool?

Regex Tester Online helps developers quickly validate regular expressions before shipping them into production code. Instead of jumping between IDE plugins and command-line tools, you can write a pattern, toggle flags, and inspect matches in real time inside one focused interface. This is especially useful when you are parsing logs, validating user input, or extracting structured data from unstructured text. The tool highlights every match, surfaces capture groups, and catches invalid patterns safely so you can iterate with confidence. Because the processing runs in your browser, it feels fast and keeps your sample text local. Use it to reduce bugs in form validation, search utilities, ETL scripts, and API integrations that rely on reliable pattern matching.

How to Use

Enter your regex in the Pattern input.
Paste sample content into Test String.
Enable flags like g, i, m, s, or u as needed.
Inspect highlighted matches and group output.
Copy matches for debugging or documentation.

Examples

Email Extraction

Input: [a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,}

Output: Matches support@company.com and dev@tool.io

UUID Detection

Input: [0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-5][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}

Output: Finds valid UUID strings in logs

Date Match

Input: \d{4}-(?:0[1-9]|1[0-2])-(?:0[1-9]|[12]\d|3[01])

Output: Matches dates like 2026-04-02

Use Cases

Validate form input patterns before release
Parse analytics, server logs, and CLI output
Extract tokens from API payloads
Debug capture groups in content migration scripts

FAQs

How do I test a regex pattern online?

Paste your pattern and sample text, then enable the correct flags. The tool highlights matches and shows group captures immediately.

What do regex flags g, i, m, s, and u mean?

g finds all matches, i ignores case, m enables multiline anchors, s lets dot match newlines, and u enables Unicode-aware matching.

Why is my regex marked invalid?

Invalid errors usually come from unescaped special characters, unbalanced brackets, or malformed groups. Update the pattern and retry.

Can I test capture groups with this regex tester?

Yes. The Match Details section lists every match index and each capture group value for fast debugging.

Is this regex tester safe for private text?

Yes. Matching logic runs in your browser, so your sample text is not sent to a backend service by default.

Input

Output

Match Details