What is a regex tester?
A regex tester (or regular expression tester) lets you write a pattern, run it against sample text, and immediately see whether it matches, where matches occur, and what went wrong if the pattern is invalid. It is the fastest way to debug expressions used in JavaScript, form validation, log parsing, data cleaning, and search-and-replace workflows — without deploying code first.
How this tool works
Dynamic Duniya’s Regex Tester uses the same RegExp engine as modern browsers (JavaScript). You enter the pattern without wrapping slashes, choose flags with checkboxes, and type or paste a test string. The page highlights every match in context and lists each matched substring with its starting character index. If the pattern cannot compile, you get an inline error instead of a silent failure.
Flags you can toggle
- Global (g): find all matches in the string, not only the first.
- Case insensitive (i): letters match regardless of upper or lower case.
- Multiline (m): ^ and $ match the start and end of each line, not only the whole string.
Who should use it?
- Developers validating email, URL, phone, or ID formats before shipping validators
- Data analysts spot-checking extract patterns on sample rows
- Students learning regular expressions with immediate visual feedback
- Anyone replacing grep-style experiments in the browser
Privacy and data
Matching runs entirely in your browser. Your pattern and test string are not sent to Dynamic Duniya servers or stored in a database. Clear the fields when you are done on a shared computer.