John Tools Lab

A collection of practical tools, experiments, and utilities I built for daily data, developer, and analysis work.

What this site is

This site is a lightweight tools hub built using Astro. The goal is simplicity, speed, and usefulness. Every tool here solves a real problem I regularly encounter in data analysis, validation, scraping, and text processing.

Tools available

Regex Tester

An Obsidian-style regex playground with live highlighting. Built to test complex patterns quickly against real-world data.

CSV Viewer

Lightweight CSV preview tool for inspecting files without opening Excel. Useful for quick validation and sanity checks.

JSON Formatter

Clean JSON formatter with syntax highlighting. Designed for API responses and debugging payloads.

Sample Size Calculator

Statistical sample size calculator with formulas displayed. Useful for surveys, experiments, and A/B testing.

What I focused on

Minimal Obsidian-inspired dark UI
Fast static delivery using Astro
No unnecessary frameworks or bloat
Tools that work fully in the browser
Self-hosted with Cloudflare protection

Why I built this

I wanted a personal lab where I could quickly build, deploy, and iterate on small utilities without overhead. This site acts as both a productivity toolkit and a living portfolio of how I approach practical problem-solving.