Question 1

What are regex flags?

Accepted Answer

Regex flags modify how the pattern matching works: g (global - find all matches), i (case-insensitive), m (multiline - ^ and $ match line boundaries), s (dotAll - dot matches newlines), u (unicode - enables full Unicode support).

Question 2

What are capture groups?

Accepted Answer

Capture groups are portions of the pattern enclosed in parentheses (). They 'capture' the matched text so you can reference it later. For example, (\d+)-(\d+) captures two groups of digits separated by a hyphen.

Question 3

How do I test my regex?

Accepted Answer

Enter your regular expression pattern in the regex field, select the desired flags, then type or paste your test string. Matches are highlighted in real-time and match details are shown below.

Question 4

What are common regex patterns?

Accepted Answer

Common patterns include email validation, URL matching, phone numbers, IP addresses, dates, and more. Use the Common Patterns sidebar to quickly insert these pre-built patterns.

Regex Tester

Regular Expression

Test String

Highlighted Matches

Match Details

Common Patterns

How Regex Testing Works

Features

Frequently Asked Questions