Free Regex Tester Online — Test Regular Expression Patterns in Real Time

A regex pattern that works in your head might not work in your code. Paste your pattern, paste your test text, and see every match highlighted with exact positions — before you commit to production. No account, no install, runs in your browser.

What the Regex Tester Does

Open Regex Tester, and you get two input fields:

1. Pattern field — type or paste your regular expression
2. Test text field — paste the string you want to match against

Every match highlights instantly as you type. You see the full match text and its start/end position in the string. Toggle JavaScript flags (g, i, m, s, u, y) to change matching behavior. Default flags: gi (global, case-insensitive).

Supported Flags

Flag	Name	What It Does	When to Use
g	Global	Find ALL matches, not just the first	Almost always — you want to see every match
i	Case-insensitive	A matches a, B matches b	Email validation, searching text regardless of case
m	Multiline	^/$ match start/end of each LINE	Log files, multi-line text where you match per line
s	DotAll	Dot (.) matches newline characters too	Matching across line breaks in HTML or templates
u	Unicode	Enables full Unicode matching	Non-Latin characters, emoji patterns
y	Sticky	Matches only at lastIndex position	Advanced: sequential token parsing

Common Patterns to Test

Pattern	What It Matches	Example Match
\\d+	One or more digits	42, 2026, 90210
\\w+@\\w+\\.\\w+	Simple email pattern	[email protected]
https?://\\S+	URLs starting with http/https	https://example.com/page
\\b[A-Z][a-z]+\\b	Capitalized words	Monday, London, Alice
\\d{3}-\\d{3}-\\d{4}	US phone format (XXX-XXX-XXXX)	555-123-4567
\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}	IPv4 addresses (basic)	192.168.1.1
^#[0-9a-fA-F]{6}$	Hex color codes	#FF5733, #00aaff
\\b\\w{8,}\\b	Words with 8+ characters	development, highlights

Who Uses a Regex Tester

• Developers — validate patterns before writing them into code (form validation, input parsing, log scraping)
• DevOps / SREs — build patterns for log analysis, grep commands, alerting rules
• Data analysts — extract patterns from CSV data, clean datasets, parse structured text
• QA engineers — verify regex in test assertions and validation rules
• Students — learn regex interactively by seeing what matches in real time
• Content managers — search-and-replace across documents using regex patterns

This Tool vs Regex101

Feature	This Tool	Regex101
Pattern matching	✓ Real-time highlighting	✓ Real-time highlighting
Match positions	✓ Start/end index shown	✓ Full match detail panel
Flags	✓ JS flags (g,i,m,s,u,y)	✓ All flags, all flavors
Regex flavors	JavaScript only	✓ PCRE, Python, Go, JS, Java
Step-through debugger	✗ Not available	✓ Full step-through
Explanation panel	✗ Not available	✓ Plain-English breakdown
Code generation	✗ Not available	✓ Generate code in multiple languages
Named group visualization	✗ Not available	✓ Visual group breakdown
Signup required	✓ None	~Optional (for saving)
Page load speed	✓ Instant (lightweight)	~Heavier (full IDE)

Regex101 is more powerful. If you need to debug a complex pattern with lookbehinds, named groups, and multi-flavor testing, use Regex101. If you need to quickly check whether a pattern matches your test data in JavaScript, this tool loads faster and has zero friction.

Workflow: Test Before You Code

1. Draft your regex pattern on paper or in your head
2. Open Regex Tester and paste the pattern
3. Paste real sample data — the actual strings you expect in production
4. Verify: does it match what it should? Does it accidentally match what it should not?
5. Adjust the pattern and flags until every match is correct
6. Copy the working pattern into your code

This catches edge cases before they become bugs. Testing against "[email protected]" is not enough — test against "hello@email", "[email protected]", and "not-an-email" to see where your pattern breaks.

Pair With Other Developer Tools

• Regex Tester — validate patterns with live matching
• JSON Formatter — format and validate JSON data you are parsing with regex
• Code Formatter — clean up code that contains regex patterns
• Diff Checker — compare text before and after regex replacements
• Find & Replace — apply regex-powered search and replace on text