Free developer tools — JWT, DNS lookup, SPF
Build a crontab or cron expression (Unix, Quartz, Kubernetes), look up DNS over HTTPS, check SPF lookup counts, decode a JWT, mint UUID v4 or RFC 9562 v7, encode Base64, URLs, HTML entities, and XML specials, convert hex ↔ RGB ↔ HSL, build CSS clamp(), simple gradients, and box-shadows, score CSS specificity, size aspect-ratio boxes, estimate password entropy, lint a .env file, hash SHA-256 or HMAC, convert chmod octal, build markdown tables, convert px to rem, parse query strings, check WCAG 2.2 color contrast, test a regex, validate JSON, convert Unix timestamps, and format XML. Queries go to public DoH resolvers or stay in this tab — nothing is uploaded to us.
Search developer
Search loads in this tab.
JWT
Hashes
MD5 Hash Generator
Free MD5 hash generator. Hash text to MD5, SHA-1, and SHA-256 in your browser. SHA uses Web Crypto; nothing is uploaded.
sha256 hash generator
Free SHA-256 hash generator. Hash text to SHA-256 (and MD5 / SHA-1) in this tab with Web Crypto. Nothing is uploaded.
hmac sha256
Free HMAC-SHA-256 generator. Sign a UTF-8 message with a key — hex and Base64, Web Crypto, in this tab. Nothing is uploaded.
password strength
Free password strength checker. Entropy from character-class pool, common-password floor, sequences — not a toy meter. Browser tool — nothing is uploaded.
Encode and decode
Base64 Encoder
Encode and decode UTF-8 Base64 or Base64url in this tab. Same alphabet JWTs use.
URL Encode Decode
encodeURIComponent and decode percent-encoded query text locally. No request is made.
query string
Free query string builder and parser. Turn ?a=1&a=2 into JSON (arrays and a[b] nests) or build a URL from pairs. Browser tool — nothing is uploaded.
html entity
Free HTML entity encoder. Encode & < > quotes, optional non-ASCII, and decode &#…; in this tab. Nothing is uploaded.
Color
CSS
px to rem converter
Free px to rem converter. 16px or custom root, reverse rem → px, and a 1–32px table. Browser tool — nothing is uploaded.
css clamp
Free CSS clamp() calculator. Fluid type from min/max px and viewports — px and rem output. Browser tool — nothing is uploaded.
aspect ratio
Free aspect-ratio box calculator. 16/9 (and presets) → CSS aspect-ratio plus the padding-bottom trick. Browser tool — nothing is uploaded.
css gradient
Free CSS gradient generator. Linear or radial from two hex stops — copy the CSS. Browser tool — nothing is uploaded.
box shadow
Free CSS box-shadow playground. Offset, blur, spread, hex color, optional inset. Browser tool — nothing is uploaded.
css specificity
Free CSS specificity calculator. IDs, classes, types — :where() is zero, :is()/:not()/:has() take the max argument. Browser tool — nothing is uploaded.
Unix
Markdown
UUID
Timestamps
JSON
Cron
Regex
XML
DNS and SPF
dns lookup checker
Free DNS lookup checker. Query A, AAAA, MX, TXT, CNAME, NS, SOA, and CAA over DNS-over-HTTPS in your browser. Nothing is uploaded.
spf record checker
Free SPF record checker. Read v=spf1 TXT records, follow includes, and count DNS lookups toward the RFC 7208 limit of 10. Browser DoH — nothing is uploaded.
Frequently asked questions
- Is it safe to paste a JWT here?
- The decoder only Base64url-decodes header and payload in your browser. Prefer expired samples. We never ask for a signing secret.
- Where do DNS and SPF queries go?
- From your browser to Cloudflare 1.1.1.1 and/or Google Public DNS over HTTPS. We do not run a nameserver and we do not see the hostname.
- Do hashes leave the device?
- No. SHA uses Web Crypto; MD5 is a local implementation.