Regex Testerv1.0.0

Enter a regular expression pattern and a test string to see every match, its captured groups, and an optional replacement result. The tool re-evaluates as you type, so you can build and refine a pattern and watch how each flag changes what it matches. Patterns run through the browser's native RegExp engine, so behavior matches JavaScript regular expressions exactly.

• Type your regular expression in the Pattern field. Enter the pattern without delimiters or flags. For example, type (\w+)@(\w+)\.(\w+) to match email-like strings.
• Paste or type the text you want to test in the Enter text to test against field. The tool supports multi-line input, so you can test patterns across paragraphs or log files.
• Click Settings to configure regex flags. Enable Global (g) to find all matches, Case Insensitive (i) to ignore letter casing, Multiline (m) to make ^ and $ match line boundaries, DotAll (s) to let the dot character match newline characters, Unicode (u) for full Unicode support, or Sticky (y) to anchor matching at the last index position.
• View results in the Results section. The tool displays the total number of matches along with each match value, its position index in the test string, and any captured groups.
• Optionally enter a Replacement Pattern to preview substitution results. Use standard replacement tokens such as $1, $2, and $& to reference captured groups and the full match. The replacement output appears in a dedicated section below the match results.
• Click Test to trigger evaluation manually, or type in any field to see results update automatically after a 500-millisecond debounce delay.
• Click Reset to clear all fields, remove saved state, and restore default settings. The tool saves your inputs and flag selections to localStorage automatically, so your work persists across page reloads.

Regular expressions drive text processing, data validation, and string manipulation across nearly every programming language and platform. Testing a pattern against representative input before it ships catches the edge cases that a hand-written regex tends to miss.

• Web Development: Validate form inputs such as email addresses, phone numbers, and postal codes by testing patterns against sample data before integrating them into client-side or server-side validation logic.
• Data Cleaning: Extract structured information from unstructured text by building capture group patterns that isolate dates, currencies, identifiers, or other tokens from raw data exports.
• Log Analysis: Parse server logs, error messages, and system output by constructing patterns that match timestamps, IP addresses, error codes, and stack trace components across multi-line entries.
• Search and Replace: Preview bulk text transformations before applying them in code editors, build scripts, or database queries by testing replacement patterns with capture group references.
• Education: Learn regular expression syntax interactively by experimenting with patterns and observing how different flags, quantifiers, and grouping constructs affect matching behavior in real time.
• Content Management: Identify and standardize formatting inconsistencies in large documents by testing patterns that detect variations in spacing, punctuation, date formats, or naming conventions.
• API Development: Build and verify URL routing patterns, parameter extraction rules, and request validation expressions used in REST API frameworks and middleware configurations.
• Security Auditing: Test input sanitization patterns to ensure they correctly detect and block potentially malicious strings, SQL injection attempts, or cross-site scripting payloads.