Regex Tester
Test regular expressions with real-time match highlighting and detailed group capture
Regex Flags Reference
| Flag | Name | Description | Example |
|---|---|---|---|
| g | Global | Find all matches instead of stopping at the first | /cat/g matches every "cat" |
| i | Case insensitive | Match regardless of upper or lower case | /hello/i matches "Hello", "HELLO" |
| m | Multiline | Makes ^ and $ match start/end of each line | /^\d+/m matches digits at line starts |
| s | DotAll | Makes . match newline characters too | /a.b/s matches "a\nb" |
| u | Unicode | Enables full Unicode matching | /\u{1F600}/u matches emoji |
| y | Sticky | Matches only at the current lastIndex position | Used for sequential parsing |
Common Regex Patterns
Click Use to load any pattern directly into the tester:
| Name | Pattern | Flags |
|---|
Frequently Asked Questions
What is a regular expression (regex)?
A regular expression is a sequence of characters that defines a search pattern. It is used to find, match, validate, or replace text. Regex is supported in virtually every programming language and text editor, making it one of the most versatile text tools available.
How do I test a regular expression?
Enter your pattern in the field above and paste your test string in the editor. Results update automatically as you type — matches are highlighted in the preview and listed below with their character position, length, and any captured groups.
What regex flags should I use?
The most commonly used flags are g (global — find all matches), i (case insensitive), m (multiline — ^ and $ match line boundaries), and s (dotAll — dot also matches newlines). Combine freely, e.g.
gi for global case-insensitive matching.How do I make a case insensitive regex?
Add the
i flag. With pattern hello and flags gi, the tester will match "hello", "Hello", "HELLO", and every other capitalization variant.Related Tools
100% Private & Secure
All regex testing runs locally in your browser. Your patterns and test strings are never sent to any server — safe for passwords, tokens, proprietary code, or any sensitive content.