Cheat Sheets

Quick reference for cron expression syntax: fields, special characters, common schedules, and platform differences (Linux, GitHub Actions, AWS, Quartz).

Complete Markdown syntax reference: headings, emphasis, lists, links, images, code blocks, tables, task lists, and GFM extensions.

Regular expression quick reference: character classes, anchors, quantifiers, groups, lookahead/lookbehind, flags, and common patterns.

Quick-reference guide to the most common Git commands — configuration, branching, merging, remote operations, undoing changes, stashing, and inspection.

Complete CSS selectors reference: basic selectors, combinators, attribute selectors, pseudo-classes, pseudo-elements, modern selectors (:is, :where, :has), and specificity.

Complete HTML reference: document structure, text tags, links, media, lists, tables, forms, inputs, and semantic HTML5 elements.

CSS Flexbox layout reference: container properties, item properties, alignment values, common patterns, and the flex shorthand.

Unix file permissions reference: octal values, symbolic notation, common chmod values, special bits (SUID, SGID, sticky), and useful commands.

JSON Web Token reference: token structure, header fields, standard claims, signing algorithms, security best practices, and common errors.