UD5 Toolkit
Markdown Diff Viewer - Online Compare & Highlight Markdown
Paste two Markdown texts and see a side‑by‑side diff with rendered preview. Perfect for editing and collaboration.
Markdown Linter - Online Check Syntax & Style
Markdown Linter
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Frequently Asked Questions
A Markdown linter analyzes your Markdown files for syntax errors, style inconsistencies, and formatting problems. It helps maintain readability, ensures compatibility across different Markdown renderers, and enforces team style guides automatically.
Common errors include: missing space after heading #, inconsistent list markers, unclosed code blocks, broken links or missing reference definitions, missing blank lines before/after headings or lists, and duplicate top-level headings.
It runs directly in your browser using JavaScript. No data is uploaded to any server. Your Markdown is parsed and checked against a set of customizable rules, and issues are displayed in real-time with line numbers and descriptions.
This tool focuses on detection. For automatic fixing, you can use tools like
markdownlint-cli --fix or editor plugins that support quick fixes. Our report helps you locate and manually correct problems.We enforce a subset of the popular markdownlint rules, including heading style, list spacing, code block closure, link validation, and blank line requirements. These align with the CommonMark and widely accepted best practices.
Pro tip: Integrate linting into your CI/CD pipeline with
markdownlint or remark-lint to enforce consistent Markdown quality across your team.
Semantic Versioning Validator - Check Semver Syntax
Validate if a version string follows SemVer 2.0.0. Also sort and compare versions. Developer tool.
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.
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.
GraphQL Schema to Markdown Docs - Online Generator
Paste a GraphQL SDL schema and get auto‑generated Markdown documentation. Perfect for API docs. All local.
Git Semver Tag Generator - Online Create Release Tags
Generate a series of semantic version tags with optional prefixes. Copy for your release script. Consistent tagging.
XML to JSON Converter - Online Parse XML to Object
Parse XML strings into compact JSON representation. Handles attributes and text nodes intelligently. Quick and private, ideal for API response translation.
YAML to JSON Converter - Online Config Translator
Translate YAML configuration files into JSON format instantly. Validate syntax during conversion. Perfect for DevOps and configuration management. Secure client-side operation.
Custom Keyboard Layout Visualizer for Touch Typing
Design a custom keyboard layout and save it as an image to help learn touch typing on a custom keymap. Supports ANSI, ISO, and ortho layouts.
NPM Version Badge Generator - Online Shields Style
Pick a package name and generate a custom version or download badge as a static image or Markdown link. For readme files.
SQL Injection Simulator - Online Educational Sandbox
Test SQL injection inputs on a mock database and see the resulting query. Learn how to prevent SQLi. No real data.
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.
Online Metronome with Subdivisions - Precise Rhythm Trainer
Play a metronome with adjustable BPM, time signature, and subdivisions (eighth, triplet, sixteenth). Tap tempo and visual flash. Works offline for practice.
Deck Baluster Spacing Calculator – Online Even Gap
Enter total rail length and baluster width to get exact spacing for code compliance. Visual layout.
PWA Icon Resizer & Manifest - Online Generate Sizes
Upload a 512x512 logo and get resized icons for every PWA requirement. Download a zip and the corresponding manifest.json snippet.
ZX Spectrum Basic Emulator - Online Retro Code Playground
Write and run simple Sinclair BASIC programs in a browser-based ZX Spectrum emulator. Load demo programs and experience 80s computing. Educational fun.
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.
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.
ARIA Attribute Validator - Online Check HTML Accessibility
Paste an HTML snippet and check for common ARIA mistakes: missing labels, invalid roles, and aria‑hidden misuse. Educate your team.
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.
SQL Syntax Validator - Online Quick Check
Paste your SQL query and check for basic syntax errors. Highlights missing commas, wrong keywords. Local analysis.
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.
Markdown TOC Generator - Online Table of Contents
Paste your Markdown and automatically generate a linked table of contents based on headings. Insert at the top. Local magic.
Code Syntax Highlighter - Online Beautiful Code Preview
Paste code and get a beautifully highlighted preview with line numbers. Supports many languages. Copy as HTML. Pure frontend.
Markdown Footnote Generator - Online Add Auto‑numbered Notes
Write text with inline footnote markers and this tool will move the notes to the bottom and add proper Markdown links. Saves time.
TOML Formatter & Validator - Online Config Tool
Check and beautify your TOML config files. Highlights errors and aligns tables and arrays. Safe local parsing.
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.
Markdown to Rich Text - Online Copy for Google Docs
Convert Markdown to styled HTML that retains formatting when pasted into Google Docs or Word. Headings, bold, lists. Client‑side.
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.