Advanced Regex Tester & Regex based file scanner

Advanced RegEx Tester instructions
🚀 What This App Does

This is a powerful, self-contained tool for building, testing, and debugging Regular Expressions (Regex). It runs entirely in your browser as a single offline HTML file. This means it's completely private (no data is sent to any server) and works even without an internet connection.

The app provides a complete environment to:

• Test patterns in real-time as you type.

• See matches highlighted directly in your test text.

• Get a detailed breakdown of all matches and capture groups.

• Perform and preview find-and-replace substitutions.

• Scan local files (.txt, .log, etc.) for all matches and download a report.

• Load complex, pre-built patterns from an extensive snippet library.

• Reference a quick-access cheat sheet for regex syntax.

• Automatically save your session to your browser's local storage.

🎯 Why Use This App?

• Complete Privacy & Security: This is the most important feature. The tool is a single, offline HTML file. No data ever leaves your computer or is sent to a server. This makes it safe to use with sensitive data, such as production logs, PII (Personally Identifiable Information), or proprietary source code. Even file scanning is done 100% in your browser; files are never uploaded.

• All-in-One Toolkit: It's more than just a validator. You get instant highlighting, detailed match and group analysis, substitution testing, and local file scanning all in one place.

• Instant Feedback for Rapid Development: See results as you type in the live tester. Every keystroke updates the highlights, match list, and replacement output. This massively speeds up the "build and test" loop for complex patterns.

• Powerful Learning & Debugging Tool: The combination of live highlighting and the detailed "Matches" breakdown (showing capture groups) makes it easy to understand why your pattern is (or isn't) working.

• Massive, Growing Snippet Library: Stop searching online for common patterns. The "Load Snippet" library provides hundreds of pre-built, tested patterns for everything from emails and URLs to specific national ID numbers and passport formats. This library will be updated over time with new and useful regex strings.

• Zero Installation & Portable: It's a single file. No installation or admin rights are needed. You can save it to your desktop, put it on a USB drive, or host it on a simple internal server for your team.

• Persistent Work: Your session (pattern, test text, and flags) is automatically saved to your browser's local storage. You can refresh the page or close the file and your work will be waiting for you.

📖 How to Use It

The interface is split into two main columns: Inputs on the left and Outputs on the right.

1. Live Tester (Main Workflow)

1. Regular Expression: Type your regex pattern in the first field (e.g., \b(\w+)\b).

2. Regex Flags: Below the pattern, check the boxes for any flags you need:

   • g (Global): Find all matches, not just the first one.

   • i (Case-Insensitive): Ignore the case (e.g., a matches a and A).

   • m (Multiline): Makes ^ and $ match the start/end of lines, not just the whole string.

   • s (dotAll): Makes the . (dot) character match newline characters as well.

   • u (Unicode): Enables full Unicode support for matching.

   • y (Sticky): Matches only from the lastIndex position (advanced).

3. Test Text: In the large "Test Text" field, type or paste the text you want to test your pattern against (e.g., Hello world).

4. Substitution (Optional): If you want to perform a find-and-replace, enter a replacement string in the "Substitution" field. You can use capture group references like $1, $2, etc. (e.g., Word: $1).

2. Understanding the Live Results

As you type, the output column and text highlighter will update automatically.

• Live Highlighting: Matched text is instantly highlighted within the "Test Text" box, giving you immediate visual feedback.

• Matches: This output box shows a detailed list of every match found. For each match, it details:

  • The full match text.

  • The index (position) where the match was found.

  • A list of all capture groups (the parts of your pattern inside parentheses (...)).

• Replacement Result: This output box shows the entire "Test Text" after your "Substitution" pattern has been applied.

3. File Scanner

This feature allows you to run your pattern against large files without pasting them into the browser.

1. Enter Your Pattern: Write or load a regex pattern in the "Regular Expression" field.

   • Note: The Global (g) flag is required for file scanning. The tool will automatically add it for the scan even if you don't check it.

2. Choose File: In the "File Scanner" box, click "Choose File" and select a local file (.txt, .log, .csv, .json, or .xml).

3. Scan & Download: Click the "Scan File & Download Report" button.

4. Get Report: The app reads the file locally (it is never uploaded) and scans its contents. A status message will appear, and a .txt report file will be automatically downloaded to your computer. This report contains a summary, the total match count, and a complete list of every match found and its capture groups.

✨ Key Features & Tools

Beyond the basic workflow, the app includes several powerful utilities:

File Scanner

This tool allows you to run your regex pattern against an entire local file without pasting its contents. It's perfect for searching through large log files or data exports. The tool generates a downloadable .txt report listing every match found, which is ideal for data mining or auditing.

Load Snippet (Pattern Library)

This dropdown menu is pre-loaded with a massive library of common and complex regex patterns.

• How it works: Simply select an entry (e.g., "Email Address," "IP Address (IPv4)," or "UK - National Insurance (NINO)").

• What it does: It automatically populates the "Regular Expression" field and sets the correct recommended flags for that pattern.

• Categories: The library is organized into groups like Web, Finance, National IDs, Passports, Postal Codes, and more.

Regex Cheat Sheet

A handy, collapsible reference guide is included in the output column. Click on "Regex Cheat Sheet" to expand a table of common regex tokens (like \d, \w, [a-z], *, +, ?) and what they mean.

Utility Buttons

• Copy: Each text area ("Regular Expression," "Test Text," "Replacement Result") has a "Copy" button. The "Copy" button for the regex pattern is special: it copies the pattern in its full /pattern/flags format (e.g., /email/gi), ready to be pasted into code.

• Clear: Each input field ("Regular Expression," "Test Text," "Substitution") has a "Clear" button to quickly empty its contents.

📚 Available Snippet Library

The "Load Snippet" dropdown provides a wide array of pre-built patterns. Here is a summary of what's available:

General

• Email Address: Finds email addresses within a block of text.

• Hex Color Code: Matches 3 or 6-digit hex codes (e.g., #fff or #FF0066).

Web & Network

• URL (HTTP/S): Finds standard web URLs.

• Extract Domain Name: A pattern with a capture group specifically for pulling the domain (e.g., google.com) from a URL.

• URL Slug: Matches common, SEO-friendly URL slugs (e.g., my-new-post).

• IP Address (IPv4): Validates a standard IPv4 address (e.g., 192.168.1.1).

• IP Address (IPv6): Matches the more complex IPv6 format.

• MAC Address: Finds hardware MAC addresses (e.g., 00:1A:2B:3C:4D:5E).

• HTML Comment: Selects HTML comments ``.

• HTML/XML Tag: Finds most HTML/XML tags (e.g., <div> or </span>).

Date, Time & Misc

• Date (YYYY-MM-DD): Matches the ISO 8601 date format.

• Date (MM/DD/YYYY): Matches the common US date format.

• Time (HH:MM or HH:MM:SS): Matches 24-hour time formats.

• International Phone (General): A broad pattern to find most international phone numbers starting with +.

• ISBN (10 or 13): Matches 10 or 13-digit ISBN book numbers.

Developer / Tech

• UUID / GUID: Matches universally unique identifiers.

• Semantic Version (SemVer): Finds software versions like 1.0.2-beta.

• File with Extension: Matches simple filenames (e.g., document.pdf).

• CSV Line: A pattern to validate or parse a single line from a CSV file.

Text Processing / Validation

• Username (Simple): A simple pattern for usernames (3-16 chars, letters, numbers, _, -).

• Password Strength (Example): An example pattern requiring 1 lowercase, 1 uppercase, 1 number, and 8+ characters.

• Match Whole Word Only: Finds a specific word, but not when it's part of another word (e.g., finds "end" but not "trending").

• Profanity Filter (Extensive): An extremely large pattern containing a vast list of profane or offensive words.

Finance (Global)

• IBAN (General): Matches the general structure of an International Bank Account Number.

• SWIFT Code: Finds SWIFT/BIC codes used for international bank transfers.

• ABA Routing Number (US): Matches US bank routing numbers.

• Credit Cards: Includes patterns for Visa, MasterCard, American Express, and Discover card numbers.

National IDs & Passports

This is the largest section, containing dozens of specific patterns for:

• National IDs (Europe): Includes patterns for Austria (ASVG), Belgium (NISS), Bulgaria (EGN), Cyprus (ID Card), Ireland (PPS), Croatia (OIB), Denmark (CPR), Estonia (Isikukood), Finland (HETU), France (INSEE/CNI), Germany (Tax ID & Identity Card), Greece (AMKA & Police ID), Italy (Codice Fiscale), Lithuania (Asmens kodas), Netherlands (BSN), Norway (Fødselsnummer), Poland (PESEL), Spain (VAT), Sweden (Personnummer), and UK (NHS/NINO).

• National IDs (North America): Includes USA (SSN, Phone) and Canada (SIN).

• National IDs (Asia-Pacific / Other): Includes Australia (TFN), Brazil (CPF & RG), China (ID Card), India (PAN & Aadhaar), Japan (My Number), South Korea (RRNO), Malaysia (NRIC), Singapore (NRIC/FIN), Vietnam (CCCD/CMND), Turkey (TC Kimlik), Qatar (QID), and UAE (ID Card).

• Passports: Provides specific passport number formats for over 20 countries, including the USA, UK, Germany, France, China, Japan (2020+), and many others.

Postal Codes

Includes specific postal code formats for:

• USA (ZIP Code)

• Canada

• UK

• Netherlands

• Sweden

• Poland

• Japan

• Brazil / South Korea

• Singapore / China / India

• Greece

• Lithuania

• And a general 4-digit and 5-digit pattern that covers many other countries (Germany, France, Spain, etc.).

Phone Numbers (Specific Countries)

Provides specific, prefixed patterns for finding phone numbers from over 30 countries, including the USA/Canada, UK, Germany, France, China, India, Japan, Brazil, and more.

Security Related (Basic)

• Potential SQL Injection: A basic pattern that looks for common SQL injection keywords (UNION, SELECT, --) and characters.

• Potential XSS (Script Tag): A simple pattern to find <script>...</script> tags.

💡 What to Expect

• Real-time Updates: Everything is live. As you type in any input field or toggle a flag, all outputs and highlights update instantly.

• Instant Error Feedback: If you type an invalid regex pattern (e.g., [a-z), a red error message will immediately appear below the pattern box explaining the syntax error (e.g., Invalid Regex: Unterminated character set).

• Session Saving: The app automatically saves your current pattern, test text, replacement string, and selected flags to your browser's local storage. If you refresh the page or close and reopen the file, your work will be exactly as you left it.