UD5 Toolkit
HTML Validator Lite - Online Check Syntax Errors
Paste HTML and detect unclosed tags, invalid nesting, and duplicate IDs. Lightweight client‑side validation.
YAML Validator & Formatter - Online Check Syntax
Waiting for input
Invalid YAML
Validate or format your YAML to see output.
Frequently Asked Questions
YAML (YAML Ain't Markup Language) is a human‑friendly data serialization standard for all programming languages.
It is commonly used for configuration files, CI/CD pipelines, and data exchange where readability matters.
This tool parses your YAML input using a robust JavaScript parser (
js-yaml).
It checks for syntactic errors, reports the exact line and column where a problem occurs,
and lets you reformat the document with consistent indentation.
Common mistakes include inconsistent indentation (mixing tabs and spaces), missing colons after keys,
incorrect list syntax, or unclosed quotes. This validator pinpoints the problematic line, helping you fix issues quickly.
Yes. The underlying parser discards comments during processing.
The formatted output will contain only the structured data without your original comments.
Absolutely. The tool supports multi‑document YAML (separated by
---).
It will report the number of documents found and the first error encountered, if any.
No. All parsing and formatting happen directly in your browser. Your YAML data never leaves your computer.
SQL Syntax Validator - Online Quick Check
Paste your SQL query and check for basic syntax errors. Highlights missing commas, wrong keywords. Local analysis.
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.
Kubernetes Deployment YAML Generator - Online K8s Spec
Fill in container image and ports. Generate a Deployment and Service YAML with best practices. Start your K8s journey.
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.
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.
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.
DNSSEC Chain Validator - Online Check RRSIG & DS
Validate a DNSSEC chain by entering DS and RRSIG records. Verify that signatures match. Educational. Local algorithm.
CSV to YAML Converter - Online Config File Generator
Paste CSV data and transform it into a well‑structured YAML array of objects. Choose key mapping. Perfect for devOps and data migration.
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.
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.
Text to Bullet Points - Online Add • or ‑ Prefixes
Paste lines and convert them into bulleted lists with symbols like •, ‑, or →. Markdown friendly. Quick formatting.
TOML Formatter & Validator - Online Config Tool
Check and beautify your TOML config files. Highlights errors and aligns tables and arrays. Safe local parsing.
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.
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.
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.
SQL Query Formatter - Online Prettify & Highlight
Upload ugly SQL and get a beautifully indented, syntax‑highlighted version. Supports multiple dialects. All local.
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.
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.
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.
SQL Formatter & Beautifier - Online SQL Query Cleaner
Format and beautify SQL queries for improved readability. Supports various SQL dialects. Quick syntax highlighting and local processing ensure a secure experience.
JavaScript Beautifier & Formatter - Online JS Code Styler
Make your JavaScript code more readable with this online beautifier. Format and indent JS automatically. Works entirely in your browser, protecting your code privacy.
CSS Beautifier & Formatter - Online CSS Organizer
Beautify and format your CSS stylesheets instantly. Organize, minify, or prettify CSS code for better readability. Processed securely on client-side.
HTML Formatter & Beautifier - Online HTML Cleaner
Tidy up messy HTML code with our online formatter and beautifier. Indent and clean your markup, preview the output instantly. No data is uploaded, everything runs in your browser.
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.