Regex Tester

Regular expressions (regex) are patterns used to match, search, and manipulate text. They are supported in virtually every programming language and are essential tools for data validation, text processing, log analysis, and search-and-replace operations. The regex syntax uses special metacharacters with specific meanings: the dot (.) matches any single character, the asterisk (*) means zero or more of the preceding element, the plus (+) means one or more, the question mark (?) means zero or one, and the caret (^) and dollar ($) anchor patterns to the start and end of strings. Character classes in brackets ([a-z]) match any character in the specified range. Quantifiers like {3} or {2,5} specify exact repetition counts. Groups in parentheses capture matched text for later reference. Lookaheads and lookbehinds assert what must (or must not) follow or precede a match without consuming characters. JavaScript regex flavors support named capture groups ((?<year>\d{4})), Unicode property escapes (\p{Letter}), and the dotAll flag (s) for dot matching newlines. The AllTools Regex Tester runs tests entirely in the browser using JavaScript's native RegExp engine — your text data never leaves your device, making it safe for testing against sensitive log data, personal information, or proprietary content.

Regular expressions solve recurring text processing challenges across development workflows. Email validation uses patterns to verify format before server-side validation — a basic pattern like /^[^\s@]+@[^\s@]+\.[^\s@]+$/ catches obvious formatting errors. URL parsing extracts protocol, domain, path, and query parameters from URL strings. IP address validation matches valid IPv4 addresses with range-aware patterns. Date parsing extracts dates in various formats (MM/DD/YYYY, YYYY-MM-DD, natural language dates) from unstructured text. Log analysis uses regex to extract error codes, timestamps, user IDs, and request paths from application logs. Code refactoring uses search-and-replace with regex to rename variables, update import paths, and restructure code patterns across large codebases. Data cleaning standardizes inconsistent formats in CSV and database exports — phone numbers, postal codes, and product codes often appear in multiple formats that regex normalizes. Password validation enforces complexity requirements with patterns checking for uppercase, lowercase, numbers, and special characters. The AllTools Regex Tester highlights matches in real-time as you type, shows capture group contents, and supports all JavaScript regex flags (g for global, i for case-insensitive, m for multiline, s for dotAll, u for Unicode).