Free · client-only · no sign-up
Developer tools.
Format JSON, decode JWTs, generate QR codes, keypairs and passwords. Everything runs in your browser — nothing is uploaded.
Formatters
JSON formatter
Pretty-print, minify and validate JSON with exact error pointers. Pasted text never leaves this tab.
Formatters
HTML / CSS formatter
Tidy indented markup or minify it for shipping. Handles inline CSS and void elements.
Encoders
Base64 encode
Encode and decode text or files with UTF-8 support and URL-safe mode. Auto-updates as you type.
Encoders
URL encoder
Percent-encode full URLs or single components, and split query strings into a readable table.
Encoders
JWT decoder
Read a JWT header and payload offline with expiry checks. Signatures are decoded, never verified here.
Generators
QR generator
Text, URL, phone or Wi-Fi credentials to a scannable QR. Download as PNG or SVG.
Generators
UUID v4
Bulk RFC-4122 v4 identifiers with cryptographically secure randomness. Copy as list, JSON or CSV.
Generators
Password generator
Random or memorable passwords with an entropy meter. Built on WebCrypto randomness.
Security
Keypair generator
RSA, EC (P-256/384/521) and AES keys via WebCrypto. Private keys stay masked until you reveal them.
Converters
Timestamp converter
Unix seconds or milliseconds to ISO, UTC and relative time — with automatic unit detection and bulk rows.
Converters
JSON to TypeScript
Infer TypeScript interfaces from JSON, with optional Zod schemas. Interface or type-alias output.
Converters
Markdown to DOCX
Convert Markdown to a real .docx file with headings, lists, tables and code. Built lazily in your browser.
Converters
Markdown to PDF
Markdown to a print-ready PDF with selectable text — styled preview, then your browser's Save as PDF.
Converters
JSX to HTML
HTML to JSX is near-lossless; JSX to HTML covers presentational components. Includes a live render check.
Converters
Mermaid diagrams
Paste Mermaid code — flowcharts, sequence diagrams and more render live. Export SVG, PNG or JPG, transparent or themed.
Text & CSS
Regex tester
Live JavaScript regex matching with flags, capture-group tables and a cheatsheet. Input-capped for safety.
Text & CSS
Color contrast
HEX, RGB or HSL pairs checked against WCAG 2.2 — AA/AAA badges plus the nearest passing shade.
🔒 Privacy — runs 100% locally
No uploads · no cookies · works offline after load. View Source if you don't believe it.
FAQ.
Is my data uploaded anywhere?
No. Every tool runs on Web APIs in this tab (TextEncoder, Canvas, SubtleCrypto, FileReader). The page works offline after first load — try it with Wi-Fi off.
Which tool should I start with?
JSON formatter and QR generator cover the most daily jobs. Keypair generator and Markdown export are the heavyweights for crypto and docs work.
Can I use generated keys and passwords in production?
Passwords and UUIDs are WebCrypto-grade and safe anywhere. Generated private keys are fine for development; for production-critical infrastructure prefer ssh-keygen or openssl in a locked-down environment.
Do the tools work on mobile?
Yes — every panel stacks vertically under the lg breakpoint, toolbars wrap, and touch targets stay at 48px minimum.