JavaScript Regex
Examples, groups, extraction, match, replace, and flags.
Learn JavaScript Regex →Learning hub
Learn Regex with examples and practice
Start with the definition, learn through practical JavaScript and number examples, then reinforce each concept with exercises, the online tester, and 24 interactive levels.
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Regex Exercises
30 practice problems with solutions from beginner to advanced.
Practice Regex →Regex for Numbers
Digits, integers, signs, decimals, ranges, and formatted values.
Learn number Regex →Regex Tester
Test patterns online and inspect matches and capture groups.
Open Regex Tester →What Is Regex? A Practical Guide with Examples
Learn what regular expressions are, what they are used for, and how to read basic patterns with practical examples.
Read guide →Regex for Beginners: Learn the Basics Without Memorizing
A beginner-friendly regex path covering literals, character classes, quantifiers, anchors, and practice.
Read guide →Regex in JavaScript: RegExp, test, match, replace and Flags
Practical JavaScript regex guide using literals, RegExp, test(), match(), replace(), and common flags.
Read guide →Regex in Python with re: search, fullmatch, findall and sub
Practical Python regex guide using the re module, raw strings, groups, extraction, and replacement.
Read guide →Email Regex: A Practical Pattern and Its Validation Limits
Learn a practical email Regex, understand each part, and see why complete email validation is more complicated.
Read guide →Brazilian CPF Regex: Validate the 000.000.000-00 Format
Regex for the common Brazilian CPF format, plus the important difference between formatting and check-digit validation.
Read guide →Brazilian CNPJ Regex: Validate the 00.000.000/0000-00 Format
Regex for the common Brazilian CNPJ format with an explanation of formatting versus check-digit validity.
Read guide →Phone Number Regex: Practical Patterns and Formatting Choices
Learn phone Regex patterns, optional formatting, international caveats, and why requirements should come first.
Read guide →URL Regex: Practical HTTP and HTTPS Examples
Learn a practical URL Regex for HTTP/HTTPS and understand protocols, domains, paths, and parsing limits.
Read guide →IP Address Regex: IPv4 Structure and Correct Validation
Learn a basic IPv4 Regex and why four numeric groups are not enough to guarantee a valid address.
Read guide →Date Regex: DD/MM/YYYY and Calendar Validation Limits
Regex examples for date formats, plus why matching DD/MM/YYYY does not guarantee a real calendar date.
Read guide →Number Regex: Integers, Signed Values, and Decimals
Practical Regex examples for digits, signed integers, decimals, and why numeric conversion still matters.
Read guide →Letters-Only Regex: ASCII, Accents, and Unicode
Regex patterns for letters only, including accented characters and Unicode considerations.
Read guide →Regex for Logs: Filter INFO, WARN, ERROR, Dates, and IDs
Use Regex to filter log levels and extract dates, IDs, and useful fields from application logs.
Read guide →20 Regex Examples to Copy, Test, and Adapt
Practical Regex examples for digits, words, email, phone, dates, URLs, files, and logs.
Read guide →Regex Exercises: A Practice Path from Beginner to Advanced
Practice Regex with progressive exercises and learn to use false positives and false negatives as feedback.
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