▸ dev.cosmolabs.org
Beautiful tools for developers
A growing collection of fast, shareable utilities for developers, designers, webmasters and engineers — plus a live showcase of CosmoLabs open source.
free forever · no login · 100% client-side
Browser Support Test
newAudit your real browser against 30 modern web capabilities — WebGPU, WASM, WebAuthn, Service Workers and more. Get a weighted readiness score, copy-paste detection snippets, and a shareable link.
/browser-support-testColor Contrast Checker
newCheck WCAG 2.2 contrast ratio between any two colors with AA / AAA pass-fail for normal and large text, plus a live preview. For accessible, on-brand design.
/contrastJSON Formatter
newBeautify, minify and validate JSON instantly. Paste, format, copy — all in your browser. Share a link to your exact input.
/json-formatterJWT Debugger
newDecode a JSON Web Token and inspect its header and payload as pretty JSON, with exp/iat claim awareness and an expiry badge. Runs entirely in your browser.
/jwtPassword Generator
newGenerate strong, cryptographically-random passwords with custom length and character sets. Shows live entropy strength. Everything runs locally — nothing is sent anywhere.
/password-generatorRegex Tester
newTest regular expressions against any text with all flags (g/i/m/s/u/y). See every match, its index and capture groups, plus the constructed pattern. 100% in-browser.
/regex-testerUUID Generator
newGenerate RFC 4122 v4 UUIDs with crypto-grade randomness. Bulk generate, copy all, toggle format (uppercase / no hyphens).
/uuidBase64 Encode / Decode
Encode text to Base64 or decode it back. UTF-8 safe, runs entirely in your browser, with a shareable link to your exact input.
/base64Case Converter
Convert text between UPPER, lower, Title, Sentence, camelCase, PascalCase, snake_case, kebab-case, CONSTANT_CASE and slug. Live, one-click copy.
/case-converterHash Generator
Compute SHA-1, SHA-256, SHA-384 and SHA-512 hashes of any text at once, using the browser's native SubtleCrypto. Copy each digest. 100% client-side.
/hashJSON ↔ CSV Converter
Convert a JSON array of objects to CSV and back. Handles quoted fields, embedded commas, newlines and escaped quotes (RFC 4180). 100% in-browser.
/json-csvLorem Ipsum Generator
Generate placeholder Lorem Ipsum text — paragraphs and sentences with adjustable counts. Classic Latin word pool, instant copy.
/lorem-ipsumNumber Base Converter
Convert numbers between binary, octal, decimal and hexadecimal. BigInt-powered, so it handles arbitrarily large values without precision loss.
/number-baseTimestamp Converter
Convert Unix epoch timestamps to human-readable dates and back. See seconds, milliseconds, ISO 8601, UTC, local and relative time at once.
/timestampURL Encode / Decode
Percent-encode or decode URLs and query parameters. Choose component (encodeURIComponent) or full-URI (encodeURI) mode. 100% client-side.
/url-encode