Guides & Cheat Sheets

Cron Expression Cheat Sheet

Quick-reference cron cheat sheet: the 5 fields, every operator (* , - /), 30 copy-paste examples with plain-English meanings, and the pitfalls that bite most.

What Is a JWT (JSON Web Token)?

How a JSON Web Token works: header, payload and signature segments, base64url encoding, the standard claims, and why decoding a JWT is not verifying it.

Common JSON Syntax Errors: 10 JSON.parse Failures and Their Fixes

The 10 most common JSON.parse failures — trailing commas, single quotes, comments, NaN — each shown broken and fixed, plus how to read the line and column.

Regex Cheat Sheet: Quick Reference

Regex cheat sheet: character classes, anchors, greedy vs lazy quantifiers, capture groups, lookarounds, flags g i m s u, plus 5 copy-ready patterns.

What Is a Unix Timestamp?

A Unix timestamp counts seconds since 1 January 1970 UTC. Learn why 1970, seconds vs milliseconds, leap seconds, the 2038 problem, and code snippets.

Markdown Cheat Sheet

Markdown cheat sheet with syntax vs result tables: headings, bold, lists, links, code blocks, GFM tables, task lists and footnotes, plus 5 copy-ready snippets.

Hex vs RGB vs HSL: Which Color Model Should You Use?

Hex vs RGB vs HSL explained: what each CSS color model encodes, a step-by-step hex to RGB to HSL conversion example, and when to use each format.

Camel Case vs Snake Case vs Kebab Case

Camel case vs snake case vs kebab case compared: rules, examples, and where each naming convention is standard in JavaScript, Python, CSS, URLs and constants.

Base64 Encoding Explained

Base64 explained: what Base64 encoding is, how 3 bytes become 4 characters, the 33% size overhead, URL-safe Base64, and why Base64 is not encryption.

MD5 vs SHA-256 Explained

Is MD5 secure? MD5 vs SHA-256 explained: digest sizes, speed, the collision attacks that broke MD5 and SHA-1, and which hash algorithm to use in 2026.

UUID Versions Explained

UUID versions explained: anatomy of the 8-4-4-4-12 format, v4 vs v7 compared, collision math, database key performance, NIL UUIDs, and which version to pick.

How to Convert PDF to Images (JPG & PNG)

Convert PDF to JPG or PNG online for free. Learn which DPI to use (72, 150 or 300), when PNG beats JPG, and how to combine images back into a PDF.

URL Encoding: Reserved and Special Characters

Percent-encoding reference: the RFC 3986 reserved characters table, encodeURIComponent vs encodeURI examples, the %20 vs + space problem, and common bugs.

Words Per Page, Speech and Reading Time

How many words per page? ~250 double-spaced, ~500 single-spaced. Convert 500-5000 words to pages, speech minutes and reading time with quick tables.

Password Entropy Explained

Password entropy explained with real math: how bits are calculated, why length beats complexity, entropy tables for 8-20 chars, and diceware passphrase tips.

HTML Entities Cheat Sheet

HTML entities cheat sheet: special character codes for &, <, >, quotes, dashes, curly quotes, arrows, math and currency symbols — named, decimal and hex.

What Is Lorem Ipsum?

Lorem ipsum explained: what the standard passage says, its real origin in Cicero's 45 BC text de Finibus, and why designers use placeholder text.