How to Generate a QR Code (and How They Work)
By qc_admin
How QR codes encode data, what error correction and the quiet zone do, which versions and modes exist, and how to make one that scans reliably.
Author: qc_admin
How to Create a Strong Password
By qc_admin
A strong password is long, random, and unique to one account. Here is why those three properties matter more than symbols and clever substitutions.
How SHA-256 Works, in Plain Terms
By qc_admin
SHA-256 pads a message, splits it into 512-bit blocks, and mixes each into a 256-bit state through 64 rounds. A plain walkthrough of every stage.
HEX, RGB and HSL Colour, Explained
By qc_admin
How HEX, RGB and HSL describe the same colours in different notations, how to convert between them, and why HSL is easier to reason about by hand.
Escaping Strings in JSON, HTML, and URLs
By qc_admin
Each context has its own escaping rules, and mixing them causes bugs and security holes. How JSON, HTML, and URL escaping differ, with worked examples.
A cURL Command Cheat Sheet for Developers
By qc_admin
The curl flags worth memorising: methods, headers, bodies, auth, following redirects, saving output, and debugging with a verbose trace.
CSV Escaping and the RFC 4180 Rules
By qc_admin
How CSV escaping really works under RFC 4180: when to quote fields, how to escape quotes and newlines, and why parsers disagree.
CSS Viewport Units: vw, vh, vmin, vmax
By qc_admin
What vw, vh, vmin and vmax measure, why 100vh caused mobile scrolling bugs, and how svh, lvh and dvh fix the moving-browser-bar problem.
Cron Schedule Examples: Every 15 Minutes, Daily, Weekly and More
By qc_admin
Copy-ready cron examples for every N minutes, hourly, daily, weekly, monthly and business-hours schedules, plus the step and range tricks behind them.
Common YAML Gotchas (and How to Avoid Them)
By qc_admin
The YAML traps that bite real projects: the Norway problem, unquoted versions and numbers, tabs versus spaces, and indentation.