Regex Tester

What is a Regular Expression?

A regular expression (regex or regexp) is a sequence of characters that defines a search pattern. Regex is used in programming, text editors, databases, and command-line tools to find, extract, or replace text based on flexible patterns rather than exact string matches.

Why Use a Regex Tester?

Writing regex patterns can be tricky — a small mistake in syntax can cause a pattern to match nothing, or worse, match the wrong things. A live regex tester lets you:

• Instantly see what your pattern matches without running code
• Debug patterns by trying different flags (global, case-insensitive, multiline)
• Inspect capture groups to verify your groups are extracting the right data
• Iterate quickly by adjusting both the pattern and test text at the same time

Common Regex Flags

• g (global) — Find all matches, not just the first one
• i (case-insensitive) — Treat uppercase and lowercase as equal
• m (multiline) — Make ^ and $ match start/end of each line
• s (dotAll) — Make . match newline characters too

Common Use Cases

• Validation: Validate email addresses, phone numbers, URLs, dates, and other formatted data.
• Extraction: Pull specific patterns from large blocks of text — IP addresses, hashtags, prices.
• Sanitization: Remove unwanted characters like extra spaces, HTML tags, or special symbols.
• Parsing: Break structured text into meaningful parts using capture groups.
• Search & Replace: Find complex patterns and replace them with dynamic substitutions.

Privacy & Security

All regex matching happens entirely in your browser using JavaScript's native RegExp engine. No text or patterns are ever sent to a server.