Regex Tester — Free Online Tool
Test regular expressions in real-time
Test regular expressions in real-time. JavaScript regex with match highlights, group capture, and explanation.
Common patterns
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Free online regex tester — JavaScript flavor, live highlighting
Toololis Regex Tester lets you test regular expressions against sample text with live match highlighting. Supports all 5 JavaScript regex flags (g, i, m, s, u), named groups, and capture groups. Everything runs in your browser — patterns and test text never leave your device.
Regex flag cheatsheet
- g (global) — Find all matches, not just the first
- i (ignoreCase) — Match regardless of upper/lowercase
- m (multiline) —
^and$match line boundaries, not just string boundaries - s (dotAll) —
.matches newlines too - u (unicode) — Enables
\p{...}unicode classes and surrogate pair handling
How to use this tool
- 1
Type your regex pattern
Enter a regular expression in the pattern field. No leading/trailing slashes needed — just the pattern itself.
- 2
Toggle flags
Click flag chips to enable g (global), i (case-insensitive), m (multiline), s (dotall), or u (unicode). Combinations work.
- 3
Paste test text
Drop the text you want to match against. Matches are highlighted live as you type.
- 4
Review matches
See the match count, individual match strings, and captured groups. Invalid regex shows a clear error message.
Common regex patterns
- Email:
\b[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}\b - URL:
https?://[^\s]+ - ISO date:
\b\d{4}-\d{2}-\d{2}\b - IPv4:
\b(?:\d{1,3}\.){3}\d{1,3}\b - Hex color:
#[0-9a-fA-F]{3,6}\b - Phone E.164:
\+?[1-9]\d{1,14}
Regex anchors & groups — quick reference
^/$— Start / end of string (or line with m flag)\\b/\\B— Word boundary / non-boundary()— Capture group(?:...)— Non-capture group (faster, no backref)(?<name>...)— Named capture group(?=...)— Positive lookahead(?!...)— Negative lookahead(?<=...)— Positive lookbehind(?<!...)— Negative lookbehind
Frequently Asked Questions
What regex flavor does this support?
RegExp engine, which is close to PCRE but not identical. Lookbehinds (?<=...), named groups (?<name>), and unicode classes \p{...} all work.What does the g flag do?
match() returns only the first match. This tool enables g by default for better visibility.What is the difference between g and m?
^ and $ match line starts/ends instead of just string start/end). They are independent — use both when searching line-by-line across a multi-line string.How do I match across newlines?
. matches any character except newlines. With s, . also matches newlines — useful for parsing HTML or multi-line blocks.Is my regex data private?
RegExp. No patterns or test text are logged, transmitted, or stored.Why is my regex slow?
(a+)+ or (.*)* can explode in time on long inputs. Use atomic groups or possessive quantifiers (not supported in JS — rewrite the pattern) or simpler expressions.Can I use capture groups?
(foo) capture text. Access them in JavaScript via match[1], match[2], etc. Named groups (?<name>foo) are accessed via match.groups.name.Key Takeaways
- Regex Tester is a free, browser-based developer tool — test regular expressions in real-time.
- No signup, no downloads, no file uploads — your data stays on your device.
- Works on desktop, tablet, and mobile. Install as a PWA for offline access.
How to Use Regex Tester
- Open the tool: Launch Regex Tester on Toololis — no account or download needed.
- Enter your data: Paste text, enter values, or select a file directly in your browser.
- Get instant results: Everything is processed locally — results appear immediately.
- Copy or download: Save your output or share it. Bookmark for quick access next time.
Regex Tester — Quick Facts
- Price
- Free — no limits, no watermarks, no paywalls
- Privacy
- 100% browser-based — no data is sent to any server
- Platform
- Any modern browser on desktop, tablet, or mobile
- Category
- Developer Tools on Toololis
- Offline
- Works offline after first visit (Progressive Web App)
| Feature | Details |
|---|---|
| Tool | Regex Tester |
| Category | Developer |
| Signup Required | No |
| File Upload | None — processed in browser |
| Mobile Support | Fully responsive |
| Cost | Free forever |
Why Use Regex Tester?
You should try Regex Tester for a quick, private way to test regular expressions in real-time. All processing happens in your browser. Your files and data never leave your device. According to web.dev, client-side processing is the gold standard for privacy.
On the other hand, dedicated APIs or desktop tools suit batch processing better. They also handle server-side automation. For everyday tasks, browser tools offer the best speed, privacy, and convenience.