Reference Command Cheatsheet
15 cheatsheets covering regex, Regex, pattern, match, http and more
Some knowledge goes unused for months and then becomes exactly what you need at 3am: how to write that regex, what that HTTP status means, how dates and timezones work, how to compare semver. These 15 sheets cover regex, HTTP methods and status codes, REST conventions, Markdown, LaTeX, ASCII codes, emoji and Unicode, MIME types, CIDR, ISO language codes, datetime and semver. When to use: pull rest-api and http-methods when writing API docs; when a request fails with 4xx or 5xx, look up the exact meaning in http-status-codes; if a regex is not matching, walk it character by character against the regex sheet; for CJK and emoji encoding issues, use the Unicode sheets. Ten minutes here before an interview, a doc review or a cross-team integration beats piecing it together from search results.
Regex Cheatsheet - Syntax, Patterns & Templates
Regex syntax and patterns: character classes like [abc], anchors ^ and $, quantifiers + and *, captured groups, and templates for email or URL.
HTTP Methods Cheatsheet - REST/HTTP Verbs & Idempotency
HTTP methods and REST semantics: GET/POST/PUT/PATCH/DELETE verbs, idempotency, safe methods, status-code pairing and common misuses. For choosing the right verb when designing APIs so retries and concurrency behave predictably. Pairs with the HTTP Status Codes sheet.
HTTP Status Codes Cheatsheet - HTTP Response Status Code Reference
Every HTTP response status code from 1xx to 5xx with its meaning, common cause and a debugging hint. Built for backend/frontend developers and Nginx/gateway ops to pinpoint why an API misbehaves — distinguishing 4xx from 5xx and checking whether redirects behave as expected.
Markdown Cheatsheet - Markdown Syntax Reference
A Markdown syntax reference covering headings, text formatting, links & images, lists, code blocks, tables, blockquotes and GFM extensions, with cross-platform caveats. For writing technical docs, READMEs and blog posts that stay clean and portable.
LaTeX Cheatsheet - LaTeX Academic Typesetting Reference
LaTeX commands for academic typesetting, grouped into document structure, text formatting, math formulas, list environments, tables/figures and references. For writing papers, reports and theses in LaTeX rather than fighting the tool.
ASCII Code Cheatsheet - ASCII Character Encoding Reference
ASCII codes for control and printable characters, each shown in decimal, hex, octal and HTML-entity forms, plus notes on Latin-1 extension and how to convert codes in common programming languages. For encoding and protocol debugging.
MIME Types Cheatsheet - Content-Type Reference
Common MIME types / Content-Type values mapped to file extensions, covering text, image, audio, video, application data, documents, archives and fonts, including charset hints. For correctly returning and validating Content-Type in HTTP responses and uploads.
HTML Character Entities Cheatsheet - HTML Special Characters Reference
HTML character entities in both named and numeric forms, for symbols, quotes, arrows, math and Greek letters. For escaping user input against XSS/breakage and for rendering special characters reliably.
Emoji Unicode Cheatsheet - Emoji Encoding Reference
Unicode codepoints for common emojis by category — smileys, gestures, hearts, animals, food and activity — plus encoding pitfalls such as surrogate pairs and ZWJ sequences. For storing and rendering emoji correctly both frontend and backend.
Screen Resolution & Aspect Ratio Cheatsheet - Device Resolution Reference
Common screen resolutions and aspect ratios grouped by phones, tablets, laptops, monitors and TVs. For planning responsive breakpoints, aligning video aspect ratios and choosing device targets.
ISO 639-1 Cheatsheet - Language Code Reference
ISO 639-1 two-letter language codes for Asian, European, Middle Eastern and African languages, each with English and native names, plus Accept-Language and HTML lang attribute usage. For wiring locale negotiation in i18n apps.
SemVer Cheatsheet - Semantic Versioning Reference
Semantic Versioning rules: the MAJOR.MINOR.PATCH structure, prerelease tags, comparison operators, npm range syntax (^ ~ >= < *) and release rules. For managing dependency versions without surprises.
RESTful API Cheatsheet - REST API Design Reference
RESTful API design conventions covering URL naming, HTTP method selection, status-code choice, request headers and response formats, auth options and best practices. For designing consistent, debuggable web APIs.
CIDR Cheatsheet - Subnet Mask & IP Address Reference
CIDR notation reference covering subnet-mask tables, common subnet sizes, private IP ranges, special-purpose addresses and the math to split or merge subnets. For network planning, ACLs and diagnosing addressing mistakes.
Date & Time Format Cheatsheet - Date Formatting & Timestamp Reference
Date & time formatting reference covering strftime tokens, ISO 8601, timezone offsets and per-language formatting methods, plus timestamp conversion and date math. For producing and parsing timestamps that don't drift across timezones.