Handbook
Learn, then practice
Structured handbooks for core developer topics—understand the subject first, then use related tools when you are ready.
DA
Data Tools
Format, validate, and transform structured data.
Data Tools
JSON Course
A structured introduction to JSON: syntax, types, parsing, generation, real-world patterns, and ecosystem tradeoffs.
Data Tools
Unix Time & Timestamps Course
Learn Unix epoch time, seconds vs milliseconds, UTC, timezones, ISO 8601, and how to debug timestamps in logs and APIs.
Data Tools
YAML Course
Learn YAML for configs and DevOps: syntax, JSON differences, Kubernetes and CI workflows, and debugging.
Data Tools
XML Course
Learn XML for configs and markup: syntax, namespaces, Maven/Android files, formatting vs validation, and debugging.
Data Tools
SQL Course
Learn practical SQL for application debugging: query structure, filtering, joins, aggregation, formatting, and common mistakes.
Data Tools
CSV and Tabular Data Course
Learn practical CSV and tabular data workflows: headers, delimiters, quoting, JSON conversion, flattening, and debugging.
Data Tools
Text Diff and Comparison Course
Learn practical text comparison workflows: line and word diff, side-by-side and unified views, config and log review, and when to use text diff vs JSON diff.
Data Tools
JSON Schema Course
Learn how JSON Schema describes data contracts, validates payloads, and evolves with APIs and configuration files.
EN
Encoding Tools
Encode and decode common developer formats.
Encoding Tools
Base64 Course
Learn Base64 encoding from first principles: binary-to-text, padding, URLs, and common pitfalls.
Encoding Tools
URL Encoding Course
Understand percent-encoding, query strings, and the difference between encodeURI and encodeURIComponent.
Encoding Tools
URL Parser Course
Learn how URLs are structured, parsed, normalized, and debugged across browsers, APIs, OAuth flows, and logs.
GE
Generator Tools
Generate IDs, passwords, and useful development values.
Generator Tools
UUID Course
Learn how UUIDs work, when to use v4, how formats differ, and what version and variant mean.
Generator Tools
Password Security Course
Learn practical password length, randomness, passphrases, storage, and sharing habits.
Generator Tools
QR Code Course
Learn how QR codes work: error correction, URL and Wi-Fi payloads, PNG output, and a pre-publish testing workflow.
WE
Web Tools
Inspect and prepare web content quickly.
Web Tools
HTML Entity Course
Learn HTML entities from first principles: escaping, named vs numeric forms, CMS workflows, and debugging.
Web Tools
Regular Expressions Course
Learn regular expressions from first principles: literals, metacharacters, flags, capture groups, replacement, and a practical debugging workflow.
Web Tools
Color for Developers Course
Learn color models for UI work: HEX, RGB, HSL, WCAG contrast, CSS formats, and a practical picking workflow.
Web Tools
Cron Expressions Course
Learn Unix cron syntax: five fields, ranges and steps, timezone traps, platform differences, common job patterns, and a practical debugging workflow.
Web Tools
Markdown Writing Course
Learn practical Markdown for developers: syntax basics, GitHub Flavored Markdown, README and issue templates, preview vs HTML export, and a reliable writing workflow.
Web Tools
CSS Units and Responsive Sizing Course
Learn practical CSS unit workflows: px, rem, em, %, vw, vh, root font-size context, clamp() fluid sizing, and debugging responsive layouts.
Web Tools
cURL Converter Course
Understand cURL commands, HTTP request parts, and the limits of converting terminal examples into fetch or Axios code.
SE
Security Tools
Inspect tokens, hashes, and security-related formats.
AI
AI Skills
Learn practical AI skills for developer workflows, prompts, coding assistants, and reliable AI-assisted work.