Developer Cheatsheets

A quick reference for regular expression syntax — anchors, character classes, quantifiers, groups, lookaheads, flags, and common real-world patterns.

A quick reference for cron schedule syntax — field definitions, special characters, and ready-to-copy expressions for common scheduling patterns.

A complete reference for HTTP response status codes — 1xx informational, 2xx success, 3xx redirection, 4xx client errors, and 5xx server errors.

A quick reference for JSON syntax — value types, object and array rules, string escapes, and the most common validation mistakes.

A quick reference for JWT structure, standard claims, signing algorithms, and common header fields.

A quick reference for common cryptographic and non-cryptographic hash algorithms — output sizes, security status, and when to use each.

A quick reference for Roman numeral symbols, values, subtractive notation rules, and conversion examples for numbers 1–3999.

A quick reference for Base64 encoding rules, alphabet, variants (standard vs URL-safe), padding, and common use cases.

A quick reference for Unix epoch time — what it is, common conversions, date math, and language snippets for working with timestamps.

A quick reference for percent-encoding rules, reserved vs unreserved characters, query string encoding, and common encoded values.

A quick reference for HTML character entities — essential escapes, symbols, currency signs, arrows, and special typographic characters.

A quick reference for CSS selector syntax — type, class, ID, attribute, pseudo-class, pseudo-element, and combinator selectors.

A quick reference for everyday Git commands — setup, staging, committing, branching, merging, rebasing, and remote operations.

A quick reference for SQL — SELECT queries, filtering, joins, aggregates, subqueries, DDL, and common functions.

A quick reference for Markdown syntax — headings, emphasis, lists, links, images, code, tables, blockquotes, and extended syntax.

A quick reference for common HTTP request and response headers — authentication, caching, content negotiation, CORS, and security headers.

A quick reference for Unix file permissions — numeric (octal) and symbolic modes, common permission patterns, and special bits.