Developer Sandbox

Free Online Developer Tools

Lightweight, secure, and 100% client-side developer utilities built to accelerate your daily software engineering workflow without compromising code privacy.

JSON Formatter & Validator

Live Tool

Instantly format, validate, and minify your JSON data online. Features interactive tree views, syntax error highlighting, and 100% local browser execution.

Open JSON Formatter →

JavaScript Minifier

Live Tool

Compress JavaScript code online in seconds. Remove unnecessary comments, whitespace, and optimize payload sizes to speed up website load times.

Open JS Minifier →

CSS Minifier

Coming Soon

Compress CSS stylesheets and reduce file size by up to 45%. Strips comments and whitespace client-side for maximum PageSpeed & Core Web Vitals optimization.

HTML Minifier

Planned

Minify HTML code online to speed up web pages. Strip comments, redundant whitespace, and inline assets securely within your browser.

Time Converter

Coming Soon

Convert Unix/Epoch timestamps to readable UTC and local date formats, and vice versa. Easily compare timezones and calculate offsets with zero server interaction.

Base64 Encoder

Coming Soon

Encode or decode text strings and raw binary files into standard Base64 format. Secure local processing ensures your sensitive assets never touch our servers.

Security & Design Principles

Our tools prioritize data privacy and workflow speed over everything else.

100% Client-Side

Your code, configuration files, and raw data are never transmitted to a backend server. Everything executes locally in your browser's sandboxed environment.

Offline Available

Because we don't rely on server APIs, our tools work fully offline. Save the page or access it without an internet connection to keep hacking.

Zero Ads & Bloat

We hate slow sites and clutter. Stacknivo Developer Tools are completely ad-free, minimal, and built using lightweight clean HTML/CSS elements.