UD5 Toolkit
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.
Validation & Verification Tools
33+ toolsSyllogism Logic Checker – Online Categorical Logic Validator
Enter two premises and a conclusion (All A are B, Some C are not B, etc.) to check validity using Venn diagram rules.
Robots.txt Validator & Parser - Online Check Syntax
Paste robots.txt content and parse it to check validity, find disallowed paths. Educational SEO tool. Local processing.
GeoJSON Validator - Online Check Geometry & Properties
Paste a GeoJSON object and validate its structure. Catch missing coordinates, wrong types, and feature errors. Local.
JSON Duplicate Key Checker – Online Find Repeated Keys
Paste JSON and instantly see if any object has duplicate keys. Quick syntax spotter.
WebVTT Subtitle Validator - Online Check Syntax
Paste a WebVTT file and instantly check for syntax errors. Validate timestamps and cue formatting. Essential for video devs.
Meta Tag Length Checker - Online Title & Description Pixel Width
See how your title and meta description will be truncated in Google SERP by pixel width. Optimize click‑through.
ARIA Label Checker – Online Paste HTML Search for Missing Labels
Paste HTML snippet and highlight interactive elements missing accessible labels. Quick a11y audit.
JWT Signature Verifier - Online HMAC/RSA/EC Check
Paste a JWT and a public key or secret to verify the signature. Supports HS256, RS256, ES256. All operations local.
Semantic Versioning Validator - Online Check Semver Syntax
Validate and compare semantic version strings. Check if a version satisfies a range (e.g., ^1.2.3). Visual breakdown of major.minor.patch. Local only.
.htaccess Validator - Online Check Syntax
Paste your .htaccess rules and check for common syntax errors or misconfigurations. No server required; static analysis.
JavaScript Syntax Validator - Online Check Errors
Paste JavaScript and catch syntax errors instantly with line numbers. Lightweight pre‑commit check. Local.
JSON-LD Validator - Online Structured Data Syntax Checker
Paste JSON-LD and validate basic syntax and required properties for Article, Product, etc. Local only. Instant feedback.
International Phone Number Formatter - Online Validate & Normalize
Paste a phone number and format it according to the E.164 standard. Identify country and detect common typos. Local parser.
Password Policy Checker - Online Test Against Rules
Define minimum length, uppercase, digits, special chars, and check if a password meets your custom policy. Instant feedback.
Crypto Address Format Checker - Online Validate Wallet
Paste a Bitcoin, Ethereum, or other crypto wallet address and quickly verify its format and checksum. No connection to blockchain.
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.
CSS Media Query Syntax Checker - Online Validator
Paste a media query and instantly check for syntax errors. See if it's correctly formed. Quick developer tool.
HTML Validator Lite - Online Check Syntax Errors
Paste HTML and detect unclosed tags, invalid nesting, and duplicate IDs. Lightweight client‑side validation.
SQL Syntax Validator - Online Quick Check
Paste your SQL query and check for basic syntax errors. Highlights missing commas, wrong keywords. Local analysis.
Weak Password Dictionary Check - Online Top 10k List
Compare your password against a built‑in list of the 10,000 most common passwords. Instant warning if it appears.
Markdown Linter - Online Check Syntax & Style
Paste Markdown and get warnings for common mistakes: inconsistent heading spacing, bare URLs, and broken links. All local.
Password Bit Strength Visualizer - Online Security Meter
Type a password and see a bar that fills based on estimated bits of entropy. Color‑coded feedback. No storage.
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.
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
Enter a URL and fetch its Twitter card meta tags. See a live preview of how the tweet will appear. Debug social sharing.
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.
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.
Semantic Versioning Validator - Check Semver Syntax
Validate if a version string follows SemVer 2.0.0. Also sort and compare versions. Developer tool.
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.
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.
Password Pwned? Checker - Online k‑Anonymity
Check if a password appears in the Have I Been Pwned database using k‑Anonymity. Only the first 5 characters of the hash are sent.
CSS Compatibility Linter - Online Check Browser Support
Paste your CSS and see warnings for properties that have limited browser support. Links to CanIUse. Modernize safely.