Regex Tester & Visualizer

Free online regex tester for JavaScript-style patterns: toggle case insensitive and global matching, inspect captures, and compare notes with Java, Python re, SQL regex, and grep-style workflows.

Last updated: 2026-04-28No data stored

Pattern (JavaScript RegExp)

Flags

Engine is browser JavaScript (similar to regexr-style checks). Java, Python re, C#, and SQL flavors differ — use this to prototype, then adapt syntax.

Sample presets

Test string

Matches

Match 1 @ index 0
```
Hello
```
Match 2 @ index 6
```
regex
```
Match 3 @ index 12
```
101
```
Match 4 @ index 18
```
test
```
Match 5 @ index 23
```
JS
```
Match 6 @ index 27
```
Python
```
Match 7 @ index 34
```
re
```
Match 8 @ index 38
```
and
```
Match 9 @ index 42
```
SQL
```
Match 10 @ index 46
```
style
```
Match 11 @ index 52
```
validation
```
Match 12 @ index 63
```
here
```

/\w+/giu

How to use

Enter your pattern and choose flags (for example case insensitive or global).
Paste sample text that should match or fail.
Review each match index, full text, and numbered capture groups.

Use cases

Prototype JavaScript regex before using regex replace in production
Compare Python re / Java / C# syntax mentally against a JS baseline
Tune phone number, IPv6-style, and starts-with patterns with live matches

Common errors

Assuming SQL REGEXP and JavaScript regex are identical
Forgetting the global flag when iterating all matches
Using unsupported lookbehind in older browser engines

FAQ

Is this the same regex engine as Java or Python?

No. This page uses the browser JavaScript RegExp engine. Syntax is often close, but Java, Python re, C#, SQL Server, and Google Sheets regex all have differences—use this tool to prototype, then port carefully.

How do I test regex replace behavior?

Use the match list to confirm your pattern first. For replace, mentally substitute each match with your replacement string, or run a quick snippet in your target language.

Does this support lookbehind?

Modern browsers support some lookbehind features, but engines vary. If a pattern fails unexpectedly, confirm support in your deployment targets.

Regex Tester & Visualizer

How to use

Use cases

Common errors

FAQ

Is this the same regex engine as Java or Python?

How do I test regex replace behavior?

Does this support lookbehind?

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Regex Tester & Visualizer

How to use

Use cases

Common errors

FAQ

Is this the same regex engine as Java or Python?

How do I test regex replace behavior?

Does this support lookbehind?

Related Tools

Try Sitemap Validator

Try Social Media Preview Checker

Try JSON to CSV Converter

Related Searches

Related Articles

How to Fix Invalid JSON Errors in APIs

Best Practices for Clean JSON in Frontend Apps

How to Decode JWT Tokens Safely