Regex Tester

Test JavaScript regular expressions in real time. Match results are highlighted as you type, with capture groups shown separately. Supports all JS flags (g, i, m, s, u, y) and replacement mode.

Regex Tester — Live RegEx Highlighting in Browser

ToolOverview

Regular expressions are the Swiss Army knife of text processing. This tool uses the ECMAScript (JavaScript) engine, supports all major flags (g / i / m / s / u / y), and highlights matches in real time. Capture groups are listed below. No IDE needed — paste your pattern and test text to debug instantly.

How to use

Type your pattern in the regex box (no / / slashes needed)
Paste your test text below
All matches are highlighted; capture groups appear underneath

Use Cases

Validating email, phone, URL, ID number formats
Extracting IPs, timestamps, and error codes from logs
Bulk find/replace workflows (combine with Diff tool)
Learning regex syntax: see cause and effect live

FAQ

Q: Which engine is used?
A: JavaScript / ECMAScript. Python / Go differ slightly (e.g. Python re supports \A).

Q: Match vs capture group?
A: Match is the whole pattern; capture groups are (...) subpatterns listed below.

Q: Common beginner pitfalls?
A: Forgetting to escape . + * ?; using \d incorrectly in string literals (write \\d).

Tips & Related Tools

Use non-greedy quantifiers to avoid over-matching: .* → .*?

Look up common patterns (email / URL / IP) in any regex cheatsheet

For complex patterns, add inline comments with (?# comment)

Common Use Cases

Use the Regex Tester Online Free online for these scenarios:

Daily work:: Bookmark this tool, use directly when needed, save time

Easy to use:: Runs in web browser, no software installation needed
Data safety:: All processing in your local browser, files not uploaded to server

Free to use:: Completely free, no signup, no watermarks, no feature limits
Cross-platform: Mac, Windows, Linux, mobile all work, just need a browser

Frequently Asked Questions

Here are the most common questions:

Q: Is this tool safe?
A: Yes. 100% client-side, data not uploaded, disappears when page closes.

Q: Do I need to register?
A: No. No login, no account, use directly.

Q: Are there usage limits?
A: No. Completely free, unlimited use.

Q: Does it support mobile?
A: Yes. All modern browsers work, including mobile.