🔍 Regular Expression Tester
Flags:
What is a Regular Expression?
A regular expression (regex) is a sequence of characters that defines a search pattern. It is widely used for pattern matching, input validation, text replacement, and data extraction. Whether you’re checking an email address, formatting a phone number, or parsing log files, regex offers a concise and powerful way to work with text.
How to Use This Tester
- Enter your regex pattern – type any valid regular expression (e.g.,
\b[A-Z][a-z]+\b). - Choose flags – toggle global (g), case‑insensitive (i), multiline (m), or dotall (s) to modify how the pattern behaves.
- Paste or type your test string – the text you want to search through.
- Click “Test Regex” – instantly see all matches highlighted, along with the total match count. If the regex is invalid, an error message will be shown.
Use the “Try example” button to pre‑fill a pattern and text, then experiment by changing the flags or modifying the regex.
Common Regex Patterns You Can Test
| Pattern | Matches |
|---|---|
\d{3}-\d{2}-\d{4} | US Social Security number (e.g., 123-45-6789) |
[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,} | Email address |
https?://[^\s/$.?#].[^\s]* | URL starting with http or https |
\b[A-Z][a-z]+\b | Capitalised words (proper nouns) |
Why Use Our Online Regex Tool?
- Instant feedback – see matches and errors as soon as you test.
- All flags supported – full control over regex behaviour.
- Clean, distraction‑free interface – focus on your pattern.
- No installation, no ads – works right inside your browser.
- Perfect for learning – ideal for beginners and experienced developers alike.
Bookmark this page and use it whenever you need to quickly validate or debug a regular expression.
