UD5 Toolkit
Test Credit Card Validator - Online Luhn Check & Issuer
Paste a test card number to verify Luhn algorithm, identify issuer (Visa, MC), and check length. No real data.
Crypto Address Format Checker - Online Validate Wallet
Crypto Address Format Checker
Instantly validate wallet address formats for 10+ cryptocurrencies
Try a sampleBitcoin
1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLyFrequently Asked Questions
It validates the format of cryptocurrency addresses including length, character set, and basic checksum patterns. For Bitcoin, it distinguishes between Legacy (P2PKH), SegWit (P2SH), and Bech32 formats. For Ethereum/BNB, it checks the 0x prefix and hex structure. It does not check if the address is active or contains funds.
BTC, ETH, BNB (BSC), LTC, BCH, DOGE, XRP, TRX, SOL. More chains are added regularly. Each coin is validated against its unique address rules (Base58, Bech32, Hex, etc.).
You may have selected the wrong coin. Also, some newer address types (like Taproot for Bitcoin) might not be recognized yet. Ensure there are no extra spaces and the address is exactly as copied from your wallet.
A checksum is a short code derived from the address data that helps detect typing errors. For example, Bitcoin uses a double SHA-256 checksum at the end of its Base58-encoded address. If you mistype one character, the checksum will likely mismatch, making the address invalid.
No, this checker only validates raw hexadecimal Ethereum addresses (0x...). It does not resolve ENS domain names.
Absolutely! All validation happens in your browser. No data is sent anywhere. You can even save the page and use it without internet.
DNS Record Syntax Checker - Online Validate BEFORE Publishing
Paste any DNS record and check if its format is valid for the selected record type (A, AAAA, CNAME, MX, TXT, SRV). Prevents typos.
HTML Validator Lite - Online Check Syntax Errors
Paste HTML and detect unclosed tags, invalid nesting, and duplicate IDs. Lightweight client‑side validation.
ETag & Last‑Modified Validator - Online Check Cache Headers
Send conditional requests to a URL and verify that the server correctly handles ETag and If‑None‑Match. Audit caching.
YAML Validator & Formatter - Online Check Syntax
Validate YAML syntax with line‑by‑line error messages. Also format messy YAML into clean, indented output. All in your browser.
SQL Syntax Validator - Online Quick Check
Paste your SQL query and check for basic syntax errors. Highlights missing commas, wrong keywords. Local analysis.
JSON Formatter & Validator - Online JSON Beautifier
Online JSON formatting and validation tool, supporting JSON minify/beautify, syntax highlighting, and error locating. Data processed locally in browser for security.
UPC Barcode Validator - Online Check Digit & EAN
Enter a UPC or EAN barcode number and validate the check digit. See if it's a real product code. Local calculation.
XML Sitemap Validator - Online Check Structure & Errors
Paste your sitemap XML and check for missing namespaces, invalid URLs, or size limit violations. Keep your SEO healthy.
XML Formatter & Validator - Free Online XML Beautifier
Easily format, validate, and beautify XML documents. Minify XML data with a single click. All processing happens locally in your browser for maximum privacy.
JavaScript Syntax Validator - Online Check Errors
Paste JavaScript and catch syntax errors instantly with line numbers. Lightweight pre‑commit check. Local.
RegEx Tester - Online Regular Expression Builder & Matcher
Build and test regular expressions against sample text. Real-time match highlighting, capture groups display, and flavor options. All inside your browser.
Luggage Size Checker - Online Airline Carry-On Compliance Tool
Enter your bag dimensions and compare against major airline carry-on and checked limits. Visual pass/fail gauge. Avoid gate fees.
Bulk Color Contrast Checker - Online WCAG Validation
Paste a list of foreground/background color pairs and instantly see which pass AA/AAA. Perfect for checking entire style guides.
Static Currency Converter - Online Fixed Rates Table
Convert currencies using a built‑in table of approximate fixed rates. Useful for quick estimates without live data. Local.
Color Contrast Checker - Online WCAG Accessibility Validator
Check the contrast ratio between foreground and background colors to ensure web accessibility compliance. Get WCAG 2.1 AA/AAA pass/fail results instantly.
Web Performance Checklist - Online Quick Audit
Answer questions about your page (image size, caching, fonts) and get a tailored list of optimization tips. Manual audit helper.
HTML Email Signature Builder - Online Professional Footer Creator
Create a polished HTML email signature with your photo, links, and company details. Live preview and copy HTML to clipboard. Works with Gmail, Outlook, Apple Mail.
Receipt & Expense Logger - Online Simple Finance
Snap or type expense details and store them locally. Categorize and see monthly totals. No cloud, no sign‑up.
Pet Sitting Checklist – Online Generate Care Sheet for Sitter
Fill in feeding, walking, medication details and generate a clear care sheet for your pet sitter. Print or share.
Audio Sample Rate Converter - Online Resample WAV/MP3
Change the sample rate of an audio file (e.g., 48kHz to 44.1kHz) without leaving the browser. Ideal for podcast prep.
Email Signature Generator - Online Professional HTML Footer
Design a clean, professional email signature with your photo, links, and disclaimers. Copy the HTML to use in Gmail/Outlook.
Even or Odd Binary Checker - Online Least Significant Bit
See how a computer decides even/odd by looking at the least significant bit. Enter decimal or binary.
Colorblind-Safe Palette Builder - Online Check & Generate Schemes
Build a palette and simulate how it appears to various color deficiencies. Also generate pre-vetted accessible palettes. Local processing.
Virtual Keyboard Tester - Online Check All Keys Functionality
Press keys on your physical keyboard and see them highlighted on a virtual keyboard. Detects multi-key rollover. Quick hardware check.
Hiking Boot Fit Checker – Online Heel Slip & Toe Room
Answer questions about fit and follow visual tests to ensure your boots are the correct size.
First Aid Kit Checklist – Online Printable Basic & Advanced
Generate a comprehensive first aid kit list for home, car, or hiking. Check off what you have.
Compost Ratio Calculator – Online Brown/Green Balance Tool
Adjust material types (leaves, grass) to achieve the ideal 30:1 C:N ratio. Improve compost bin performance. Local only.
Math Expression Evaluator - Online Type & Calculate
Type a mathematical expression like 'sqrt(16)+sin(pi/2)' and get the result instantly. Supports popular functions. Local.
Palindrome Checker - Online Test Words & Sentences
Check if a word or phrase is a palindrome (reads same forward and backward). Live validation and fun facts.