Quick References
One-page developer cheat sheets you can print or keep open — each paired with a free tool that runs in your browser.
⏰ Cron Cheat Sheet
The five fields, special characters, 27 ready-made schedules, and cron in GitHub Actions, Kubernetes and AWS.
Open cheat sheet →📋 JSON Cheat Sheet
Data types, syntax rules, escapes, and every common JSON.parse error with its fix.
Open cheat sheet →🔑 JWT Cheat Sheet
Claims, header fields, HS256 vs RS256, a security checklist and verification code.
Open cheat sheet →⏱ Unix Time & Date Formats
Seconds vs milliseconds, notable timestamps, ISO 8601 and RFC 2822, strftime codes.
Open cheat sheet →🔗 URL Encoding Cheat Sheet
Percent-encoding table, UTF-8 examples, encodeURI vs encodeURIComponent.
Open cheat sheet →🆔 UUID Cheat Sheet
Versions v1 to v8 with examples, which to choose, and v4 and v7 in 8 languages.
Open cheat sheet →🔐 Base64 Cheat Sheet
How encoding and padding work, the alphabet, URL-safe Base64, and spotting PNG, PDF and JWT data.
Open cheat sheet →🔤 HTML Entities Cheat Sheet
Characters to escape, named, decimal and hex codes for symbols, and escaping by context.
Open cheat sheet →🔑 Hash Algorithms Cheat Sheet
MD5 vs SHA-1 vs SHA-256, test values, password hashing, HMAC and file checksums.
Open cheat sheet →📐 YAML Cheat Sheet
Syntax, value types, | and > multi-line strings, anchors, and gotchas like the Norway problem.
Open cheat sheet →Each quick reference fits on one printable page and links to a matching tool, so you can look something up and try it straight away. Bookmark this page — more references are on the way.