Regex Tester
Test regular expressions in real-time with match highlighting.
Regular expressions are among the most powerful and most confusing tools in a developer's arsenal. This tester lets you write a regex pattern, see matches highlighted in real time, inspect captured groups, and test replacements — all with instant visual feedback. It supports JavaScript regex syntax with global, case-insensitive, and multiline flags.
How to Test a Regular Expression
- Enter your pattern — type your regex in the Pattern field (without slashes). Example:
\b\w+@\w+\.\w+\b - Set flags — use
gfor global,ifor case-insensitive,mfor multiline. Default isgmi. - Enter test string — paste the text you want to match against.
- See results instantly — matches are highlighted, the match count shows, and each match with its position and groups is listed below.
Frequently Asked Questions
What regex flavour does this tester use? ▼
This tester uses JavaScript (ECMAScript) regular expressions, which run natively in all modern browsers. Patterns follow the standard JS regex syntax. Supported flags: g (global), i (case-insensitive), m (multiline), s (dotAll), u (unicode).
What do the regex flags g, i, m mean? ▼
g — global: find ALL matches (not just the first). i — case-insensitive: match regardless of case. m — multiline: ^ and $ match start/end of each line, not just the whole string. s — dotAll: the . character also matches newline characters.
What is a capture group in regex? ▼
Capture groups are portions of a regex in parentheses, e.g.
(\d{4})-(\d{2})-(\d{2}) captures year, month, and day separately from a date string. This tool shows captured groups in the Match List.How do I make my regex case-insensitive? ▼
Add the
i flag. In the Flags field, type gi or gmi. With the i flag, /hello/i matches "Hello", "HELLO", "hElLo", etc.How do I match a whole word (not partial)? ▼
Use word boundaries
\b around your pattern. For example, \bcat\b matches "cat" in "the cat sat" but not in "category". \b marks the transition between a word character (\w) and a non-word character.Common Regex Patterns
Email:
URL:
Phone:
IP Address:
HTML Tag:
Hex Color:
Date (YYYY-MM-DD):
Postal Code (UK):
\b[\w.-]+@[\w.-]+\.\w{2,}\bURL:
https?://[^\s]+Phone:
\+?[\d\s()-]{7,}IP Address:
\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\bHTML Tag:
<[^>]+>Hex Color:
#[0-9a-fA-F]{3,8}\bDate (YYYY-MM-DD):
\b\d{4}-\d{2}-\d{2}\bPostal Code (UK):
[A-Z]{1,2}\d{1,2}[A-Z]?\s?\d[A-Z]{2}