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Notes on JSON, regex, JWTs, and other things you forget between jobs.

8 posts · 2026

#008

QR codes beyond URLs — WiFi, vCard, payment

QR code structure, error correction, WiFi and vCard formats, capacity limits, and generator tips.QR Code Generator7 min read#007

YAML vs JSON — readability vs tooling

When YAML helps, when it hurts (the Norway problem), and how to choose between the two for config and APIs.YAML ↔ JSON Converter7 min read#006

JWT security — what to check before trusting a token

JWT structure, the alg:none attack, RS256/HS256 confusion, expiry validation, and safe storage practices.JWT Decoder8 min read#005

Cron expressions explained in plain English

The five fields, special characters, common schedules, and the gotchas that trip people up.Cron Expression Builder8 min read#004

UUID v4 vs v7 — which should you use?

How v4 and v7 UUIDs are generated, why v7 is better for database primary keys, and when v4 is still fine.UUID Generator7 min read#003

Writing better regular expressions

Common regex mistakes, practical patterns for everyday validation, and tips for avoiding catastrophic backtracking.Regex Tester8 min read#002

Base64 encoding — what it is, when to use it, when to avoid it

How Base64 works under the hood, where it belongs (data URLs, JWTs, email), and why it is not encryption.Base64 Encoder/Decoder8 min read#001

How to validate JSON at the command line and in the browser

Practical ways to validate JSON using jq, python, Node.js one-liners, browser DevTools, and online tools.JSON Formatter7 min read