Reference
Quick lookup sheets for the things you check rather than read. No long explanations, just grouped tables you can scan.
51 references
28 entriesHTTP status codesA complete, grouped reference of HTTP status codes — 1xx informational, 2xx success, 3xx redirects, 4xx client errors, and 5xx server errors — with plain meanings.Open
8 entriesHTTP methods referenceA reference of HTTP request methods — GET, POST, QUERY, PUT, PATCH, DELETE, and more — with their typical use and whether they are safe and idempotent.Open
16 entriesCommon HTTP headers referenceA reference of common HTTP request and response headers — content, caching, auth, and CORS — with what each one does.Open
17 entriesURL encoding referenceA percent-encoding lookup table for URLs: common reserved and unsafe characters and their %XX escape codes, plus when to encode.Open
26 entriesMIME Types List and Content-Type LookupA quick lookup list of common MIME types and Content-Type values by category, with file extensions for text, images, audio, video, fonts, and application formats.Open
12 entriesCSS units referenceA reference of CSS length units — absolute, font-relative, and viewport-relative — plus when to use each for responsive, accessible layouts.Open
8 entriesCSS color formats referenceA reference of CSS color notations — HEX, RGB, HSL, named colors, and modern formats — with an example of each and when to use it.Open
15 entriesHTML entities referenceA reference of common HTML entities — reserved characters, punctuation, symbols, and spaces — with their named and numeric codes to copy.Open
27 entriesGit commands cheat sheetThe everyday Git commands grouped by task — setup, staging and committing, branching, working with remotes, and undoing changes — each with a one-line explanation.Open
40 entriesRegex cheat sheetA scannable reference of regular expression syntax: character classes, quantifiers, anchors, groups, and lookarounds, each with what it matches.Open
21 entriesASCII tableA reference of ASCII character codes: printable characters and key control codes, each with its decimal and hexadecimal value.Open
16 entriesJSON Schema keywordsA reference of common JSON Schema keywords for types, objects, arrays, numbers, and strings, with what each one constrains.Open
16 entriesCron quick referenceA reference of cron syntax: the five fields, the special characters, and ready-to-use schedule examples you can copy.Open
14 entriesMarkdown cheat sheetA copy-paste reference of Markdown syntax: headings, emphasis, lists, links, images, code, quotes, and tables.Open
23 entriesDate format tokens referenceA reference of date and time format tokens for strftime (Python, C, PHP) and the Unicode tokens used by date-fns and Day.js.Open
4 entriesHash algorithms referenceCommon hash algorithms compared — MD5, SHA-1, SHA-256, SHA-512 — with output size, hex length, and whether they are safe to use for security.Open
4 entriesUUID versions referenceThe UUID versions compared — v1, v4, v5, and v7 — with what each is based on, whether it sorts by time, and when to use it.Open
5 entriesSQL join types referenceThe SQL join types compared — INNER, LEFT, RIGHT, FULL, and CROSS — with which rows each keeps and when to use it.Open
9 entriessecurity.txt fields reference (RFC 9116)Every security.txt field from RFC 9116 — Contact, Expires, Encryption, Policy, Canonical, and more — with which are required, which may repeat, and what each is for.Open
8 entriesrobots.txt directives referenceEvery robots.txt directive — User-agent, Disallow, Allow, Sitemap, and Crawl-delay — with what it applies to, what it does, and which crawlers honor it.Open
9 entriessitemap.xml tags referenceThe XML tags for a sitemap and a sitemap index — urlset, url, loc, lastmod, changefreq, priority — with which are required and the size limits.Open
9 entrieshumans.txt fields referenceThe conventional humans.txt sections and fields — TEAM, THANKS, and SITE — with what each line is for. humans.txt is an informal convention, not a standard.Open
11 entriesOpen Graph & Twitter Card tags referenceThe Open Graph (og:) and Twitter Card meta tags for link previews — title, description, image, url, type, and card — with which are required and the recommended sizes.Open
7 entriesllms.txt structure referenceThe parts of an llms.txt file — H1 name, summary blockquote, H2 link sections, and the Optional section — with the Markdown format and where the file goes.Open
14 entriesJWT claims referenceThe registered JWT claims from RFC 7519 — iss, sub, aud, exp, nbf, iat, jti — plus the header fields and what each value means.Open
6 entriesImage formats referenceA quick comparison of PNG, JPG, WebP, AVIF, GIF, and SVG — compression type, transparency support, and what each format is best used for.Open
10 entriesUnit conversion referenceCommon length, mass, and temperature conversion factors between metric and imperial units — km to miles, kg to pounds, Celsius to Fahrenheit, and more.Open
6 entriesAspect ratios referenceCommon aspect ratios with example resolutions and where each is used — 16:9, 4:3, 1:1, 9:16, 21:9, and 3:2.Open
12 entriesTime zones referenceCommon time zones with their abbreviations and standard UTC offsets — ET, CT, PT, GMT, CET, IST, JST, and more, with a note on daylight saving.Open
8 entriesBMI categories referenceThe standard WHO adult BMI categories — underweight, normal, overweight, and obese — with their exact ranges and the BMI formula.Open
5 entriesToken estimates referenceRough token conversions for AI models — tokens per word, per character, and per page of English — plus why code and other languages differ.Open
6 entriesPrompt Template Parts ReferenceA compact reference for prompt template sections: task, context, audience, output format, constraints, examples, and quality checks.Open
6 entriesAI Output Formats ReferenceChoose practical AI output formats such as Markdown, JSON, tables, outlines, CSV, and YAML, with checks before copying into a workflow.Open
5 entriesChat Export Cleanup ReferenceCommon AI chat export patterns, what to remove before reuse, and what to keep when speaker context matters.Open
5 entriesTranscript Cleanup Rules for AI PromptsTimestamp, speaker label, filler word, and caption cue cleanup rules for preparing transcripts before AI prompt use.Open
5 entriesMarkdown for AI Prompts ReferencePractical rules for cleaning Markdown before AI prompt use, including frontmatter, comments, fences, links, and spacing.Open
10 entriesSocial media image sizes referenceRecommended image dimensions for Instagram, YouTube, X, Facebook, LinkedIn, and TikTok — posts, stories, thumbnails, and banners in pixels.Open
4 entriesYouTube Chapter Rules ReferenceQuick YouTube chapter timestamp rules: start at 00:00, use at least three timestamps, keep them in order, and avoid chapters shorter than ten seconds.Open
7 entriesYouTube Thumbnail Specs ReferenceYouTube thumbnail size, ratio, file format, and upload-limit reference for Studio desktop, mobile upload, and the YouTube Data API.Open
6 entriesSRT and VTT Caption Format ReferenceQuick SRT and WebVTT caption format lookup for cue numbers, timestamp lines, text lines, and common cleanup mistakes.Open
7 entriesAudio formats referenceA comparison of common audio formats — MP3, WAV, FLAC, AAC, M4A, OGG, and Opus — with compression type and what each is best used for.Open
8 entriesVideo formats & codecs referenceThe common video containers — MP4, WebM, MOV, MKV — and codecs — H.264, H.265, VP9, AV1 — with what each is best for and how well browsers support them.Open
18 entriesCSS Flexbox cheat sheetA reference of CSS Flexbox properties for the container and the items, with what each one controls and common values.Open
17 entriesCSS Grid cheat sheetA reference of CSS Grid properties for the container and items, plus the track-sizing units you use to build two-dimensional layouts.Open
20 entriesCSS selectors cheat sheetA reference of CSS selectors: type, class, id, attribute, combinators, pseudo-classes, and pseudo-elements, with what each one targets.Open
7 entriesHTTP security headers referenceA reference of the HTTP security headers worth setting, with a recommended value to copy and what each one protects against.Open
12 entriesPermissions-Policy directives referenceCommon Permissions-Policy features — camera, microphone, geolocation, and more — plus the allowlist values that enable or disable them.Open
14 entries.gitignore patterns referenceA reference of .gitignore syntax and common patterns, plus copy-paste starter blocks for Node, build output, and environment files.Open
13 entriesGit config referenceA reference of useful git config settings: identity, defaults, editor, line endings, and handy aliases, each ready to copy.Open
13 entriesURL tracking parameters referenceA reference of common URL tracking parameters — UTM tags and click identifiers — that you can safely strip from a link before sharing it.Open
7 entriesFile metadata by type referenceA reference of what hidden metadata common file types carry — photos, PDFs, documents, audio — and how to remove it before sharing.Open