Why I stopped using random online tools (and built my own 100% local alternative)

cancerdude — Sat, 19 Sep 2026 15:57:10 +0000

As developers, we constantly rely on quick online utilities. Need to format a messy JSON payload? Decode a JWT token? Compare two code snippets? Generate a UUID? We just Google it, click the first result, and paste our data in.

But recently, I had a terrifying thought while pasting a production API key into a random JSON formatter: "Wait, is this site logging my data?"

The truth is, many free online tools process your data on their backend servers. You have absolutely no guarantee that your proprietary code, API keys, or sensitive customer data isn't being saved, logged, or worse, leaked.

The Solution: Building a 100% Local Toolset

I decided to stop trusting random servers and build FastUtilz — a collection of developer and everyday utilities where absolutely zero data ever leaves your device.

By leveraging modern Web APIs, JavaScript, and WebAssembly, I was able to build tools that do all the heavy processing directly in your browser.

The Tech Stack

I wanted this site to be blazing fast, so I chose a modern stack:

Astro - To ship zero JavaScript for the static pages and ensure instant load times. Components only hydrate when absolutely necessary.
Vanilla CSS - No heavy frameworks, just a clean, developer-focused true dark mode (#0b0e14).
Cloudflare Pages - For lightning-fast global edge hosting.

The Tools (So far)

I've built 14 tools so far, completely free and instantly usable. Here are some of the most popular ones:

👨‍💻 Developer Tools:

JWT Decoder - Safely inspect your tokens.
JSON Formatter & Beautifier - Format massive payloads instantly.
Text Diff Checker - Find differences in code or text files side-by-side.

🖼️ Image & Media Tools:

Image Compressor - Shrink file sizes entirely in-browser.
Base64 Encoder / Decoder
QR Code Generator

📝 Formatting & CSS:

Try it out!

You can check out the full collection here: FastUtilz Homepage

I'm actively maintaining this and looking to add more tools that developers actually need. What is the one utility you find yourself constantly Googling for? Let me know in the comments and I'll add it to the platform!

DEV Community: cancerdude

Why I stopped using random online tools (and built my own 100% local alternative)

The Solution: Building a 100% Local Toolset

The Tech Stack

The Tools (So far)

Try it out!