UD5 Toolkit
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.
Twitter Card Previewer - Online See How Tweets Render
Twitter Card Previewer
Live Preview
@handle
Card Title Preview
Description will appear here
Summary Large Image
Frequently Asked Questions
A Twitter Card is a rich preview that appears when a link is shared on Twitter. It includes a title, description, image, and other media, making tweets more engaging. Twitter Cards are powered by meta tags in the page's HTML.
Simply fill in the fields on the left with your desired Twitter meta tag values. The live preview on the right updates instantly. Choose between desktop and mobile views. Once satisfied, click “Copy Meta Tags” to get the HTML code to paste into your website's
<head>.This tool previews Summary, Summary with Large Image, App, and Player cards. Each type has different visual layouts and required meta tags. Select the desired type from the dropdown to see the relevant fields.
Make sure the image URL is absolute (starts with
https://) and accessible. If the image fails to load, the previewer shows a placeholder icon. Twitter also requires images to be at least 144x144px (300x157px for large image cards) and under 5MB.Use Twitter's official Card Validator once your page is publicly accessible. Paste the URL and Twitter will fetch the latest meta tags. Remember to clear cache if you've updated the tags.
Yes. Adding Twitter Card meta tags to your HTML does not require any API key or developer account. They are standard
<meta> tags recognized by Twitter's crawler.Event Schema Markup Generator - Online JSON‑LD for Concerts
Build a complete Event structured data with performer, location, and dates. Get Google‑ready JSON‑LD for tickets.
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.
DNSSEC Chain Validator - Online Check RRSIG & DS
Validate a DNSSEC chain by entering DS and RRSIG records. Verify that signatures match. Educational. Local algorithm.
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.
Keyword Extractor - Online Rapid Text Analysis
Paste any article and get a list of the most relevant keywords using a simple TF‑IDF‑like model. Skip stop words. All local.
ISBN Validator - Online Check ISBN‑10 & ISBN‑13
Validate ISBN‑10 and ISBN‑13 numbers and compute their check digits. Useful for booksellers and libraries. All local.
Live Website Audit Checker - Online Quick SEO & Performance
Enter a URL and get a one‑page report of titles, description, headings, image alts, and broken links. All from browser.
IBAN Structure Checker - Online Validate Format & Country
Check if an IBAN has the correct length and structure for its country. Early validation, no bank connection.
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.
HTML Outline Extractor - Online Heading Map from URL
Enter a URL and see a nested list of all h1‑h6 tags. Check document structure for SEO and accessibility.
Font Size Scale Preview - Online Typography Visualizer
Type a few words and see them rendered at every heading size (h1–h6) with your chosen font. Perfect for design systems.
Favicon Checker - Online Test Any Site's Icon
Enter a URL and see its favicon at all standard sizes. Check if it's properly defined. SEO basic check.
Semantic Versioning Validator - Check Semver Syntax
Validate if a version string follows SemVer 2.0.0. Also sort and compare versions. Developer tool.
Markdown Linter - Online Check Syntax & Style
Paste Markdown and get warnings for common mistakes: inconsistent heading spacing, bare URLs, and broken links. All local.
HTTP Redirect Path Tracer - Online SEO Chain Analyzer
Trace the full redirect path of a URL. See every hop, status code, and final destination. Detect broken chains.
Robots.txt Validator - Online Check Syntax & Rules
Paste a robots.txt file and validate its syntax. See if a specific user‑agent can access a path. Essential for webmasters.
CMYK Color Preview - Online See Print vs Screen
Preview how a CMYK value will look on screen (approximate). Compare with its RGB equivalent. Pre‑press check.
Base64 String Validator - Online Check Valid Encoding
Paste a string and verify if it is valid Base64. Auto‑detects padding issues and character errors. Quick dev check.
HTML Includes Previewer - Online Simulate SSI Includes
Paste multiple HTML snippets (header, footer) and a main content, then combine them into a single preview. Static site helper.
Quilt Pattern Previewer - Online Fabric Layout Visualizer
Arrange virtual fabric squares or triangles on a grid to preview a quilt pattern. Change colors and sizes. Export layout.
Swagger/OpenAPI YAML Previewer - Online Render & Test
Paste your Swagger/OpenAPI YAML and see a rendered API documentation preview with expandable endpoints. All local rendering.
PRNG Validator - Online Check Randomness Pattern
Paste a list of numbers to visually check uniformity, mean, and simple pattern analysis. Educational tool for statistics and RNG.
Open Graph Debugger - Online Fetch & Preview Social Card
Enter a URL to see exactly what Open Graph and Twitter card tags will be shown when shared on social media. Fetch from browser.
Lottie Animation Previewer - Online JSON Player
Paste Lottie JSON code or upload a .json file and see the animation play. Control speed and loop. Perfect for developers.
Redirect Path Tracer - Online SEO Redirect Chain Analyzer
Enter a URL and trace the full redirect chain, seeing each hop's status code and location. Identify unnecessary redirects. Client-side fetch.
Robots.txt Generator - Online Create & Validate Robots File
Build a properly formatted robots.txt file with user-agent rules and sitemap location. Validate syntax in real time. Essential for webmasters.
XML Sitemap Generator - Online Free Website Sitemap Builder
Generate a standard XML sitemap for your website by entering a start URL. Crawls internal links directly from your browser. No server-side processing.
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.
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.