RegEx Tester & Visualizer
Write and test regular expressions in real-time. Visualize match results and debug capturing groups locally.
What are Regular Expressions (RegEx)?
A **Regular Expression (RegEx)** is a sequence of characters that forms a search pattern. It is used to perform pattern-matching, input validation, search-and-replace operations, and lexical analysis across almost every programming language.
Common use cases include verifying whether user inputs are formatted correctly (like email validation, phone number structures, or password strength criteria) or parsing server logs to extract specific key values.
Understanding RegEx Flags
Flags alter the matching behavior of the regular expression:
- g (Global): Continues matching beyond the first match, identifying all occurrences in the text.
- i (Case-insensitive): Ignores capitalizations (e.g.
/[a-z]/imatches "A" and "a"). - m (Multiline): Makes the start
^and end$boundary anchors apply to each individual line, rather than just the beginning and end of the entire string. - s (dotAll): Allows the dot character
.to match newline characters (\n). - u (Unicode): Treats the pattern as a sequence of unicode code points, necessary for parsing emojis and complex international symbols correctly.
Frequently Asked Questions
A regular expression is a sequence of characters that forms a search pattern. When you search for data in text, you can use this search pattern to describe what you are looking for, such as verifying emails, parsing logs, or replacing text.
We support the standard ECMAScript JavaScript flags: Global (g) to search all matches, Case-insensitive (i), Multiline (m) for line anchor matches, dotAll (s) to allow dots to match newlines, Unicode (u) for full unicode parsing, and Sticky (y) for anchored searches.
No. The regex validation and execution occur entirely inside your browser's local sandbox using the Vercel-free, standard client-side V8 RegExp engine.