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Quick-reference guides for developers. Accurate, concise, and printable.
Complete regular expression reference with character classes, quantifiers, anchors, groups, lookaheads, and flags. Quick-reference for pattern matching in JavaScript, Python, PHP, and more.
Complete CSS Flexbox reference covering container properties, item properties, alignment, and common layout patterns. The essential one-page guide for flexible box layouts.
Complete CSS Grid reference with template definitions, item placement, alignment, and common layout patterns for two-dimensional grid layouts.
Complete Markdown syntax reference covering headings, emphasis, lists, links, images, code blocks, tables, and extended syntax. Works with GitHub, GitLab, and most editors.
Complete reference of HTML character entities including special characters, mathematical symbols, arrows, currency signs, and common typographic marks.
Complete Linux/Unix file permissions reference covering numeric (octal) notation, symbolic notation, common permission patterns, and special modes like setuid and sticky bit.
Complete cron expression reference with field definitions, special characters, common schedules, and real-world examples for scheduling jobs on Linux, macOS, and CI/CD platforms.
Complete JSON reference covering data types, syntax rules, escape characters, common patterns, and validation tips. Essential for APIs, configuration files, and data interchange.
Complete SQL reference covering SELECT, WHERE, JOIN, GROUP BY, subqueries, and common functions. Works with MySQL, PostgreSQL, SQLite, and SQL Server.
Complete reference of HTTP status codes organized by category: 1xx informational, 2xx success, 3xx redirection, 4xx client errors, and 5xx server errors with descriptions.