Open Graph Preview
Fill in meta info and preview share card style (local simulation).
robots.txt Generator
Check common rules and generate robots.txt text.
Sitemap Generator
Generate sitemap.xml fragment from URL list.
CSP Builder
Toggle Content Security Policy directives and export header value.
Permissions-Policy
Feature policy header builder with explanations.
.env Parser
Paste env file and view as table (one-click value masking).
Security Headers Cheat Sheet
Common HTTP security header descriptions and one-click copy examples.
URL Parser
Decompose URL and query parameters into a table.
Punycode
Internationalized domain name xn-- and Unicode.
Data URL
Convert between file and data: Base64.
File Type Sniff
Guess type by magic bytes (PNG/PDF/ZIP etc.).
MIME Lookup
Extension and MIME type reference.
HTML Formatter
Indent and minify (js-beautify).
SVG Formatter
SVG/XML validation and indentation.
Markdown ↔ HTML
Preview rendered output and export.
HTTP Status Codes
Common codes lookup and search.
User-Agent
Rough UA string parsing.
Key Code
Debug keydown key / code values.
Color Converter
Convert between HEX, RGB, HSL and copy as CSS.
Color Contrast
WCAG foreground/background contrast ratio.