Question 1

What is a Regular Expression (Regex)?

Accepted Answer

A regular expression is a sequence of characters that specifies a search pattern in text. It's used by developers for string searching, text replacement, and input validation.

Question 2

How does the Regex Tester work?

Accepted Answer

Enter your regex pattern at the top, select your flags (like 'g' for global or 'i' for case-insensitive), and type or paste text into the Test String area. The tool will instantly highlight matching text.

Question 3

What are Regex flags?

Accepted Answer

Flags change how the regex engine searches. Common flags include 'g' (global search to find all matches rather than stopping after the first), 'i' (case-insensitive search), and 'm' (multiline search where ^ and $ match start/end of lines).

Question 4

Is my text sent to a server?

Accepted Answer

No. The Regex Tester executes the JavaScript RegExp engine entirely within your browser. None of the text you paste or type is ever transmitted or logged, guaranteeing total privacy.

Question 5

What if my Regex causes an infinite loop?

Accepted Answer

Our engine uses standard safety limits and bounds checking on zero-width global matches to prevent your browser from crashing during bad pattern evaluations.

Regex Tester

Expression Editor

Common Patterns

Cheat Sheet

Professional Pattern Validation

Frequently Asked Questions

Client-Side Validation Engine

Explore More Free Tools

JSON Formatter

JWT Decoder

Text Case Converter