There are already hundreds of online developer tools.

JWT decoders, JSON formatters, Base64 encoders, regex testers, hash generators—you can find them everywhere.

So why build another one?

The Problem

While working on frontend projects, I found myself constantly opening different websites for simple tasks:

Decode a JWT token
Format JSON
Test a regular expression
Encode a URL
Generate a QR code

Most tools worked, but many had one or more of these issues:

Too many ads
Slow loading times
Overcomplicated interfaces
Data being sent to remote servers

For quick development tasks, I wanted something simpler.

My Goal

The goal was straightforward:

Fast
No signup
Minimal UI
Multi-language support
Browser-first processing

Whenever possible, processing happens directly in the browser.

That means your JSON, JWTs, text, and other data don't need to leave your device.

Tech Stack

The project is built with:

React 19
TanStack Start
TypeScript
Tailwind CSS

The site currently supports:

English
Korean
Japanese
Chinese
Current Tools

Some of the available tools include:

JWT Parser & Generator
JSON Formatter
Base64 Encoder / Decoder
URL Encoder / Decoder
Hash Generator
Regex Tester
QR Generator
Barcode Generator
Color Tools
Cron Parser
Sitemap Validator
What I Learned

The most interesting part wasn't building the tools themselves.

It was learning how many small usability details matter:

Copy buttons
Mobile layouts
Keyboard shortcuts
Localization
SEO for utility pages

These tiny details often take longer than the core functionality.

What's Next

I'm continuing to add new tools and improve the existing ones.

If you've built similar utility websites, I'd love to hear what features users found most useful.

Website:
https://lets-tools.com