I Built 30+ Free Web Tools with Zero Server Uploads (100% Client-Side)

Mecso — Sun, 23 Aug 2026 16:40:29 +0000

Most online utility sites (PDF converters, image optimizers, file format converters) force you to do two things I really dislike:

Upload private documents (contracts, invoices, ID cards, tax receipts) to unknown third-party cloud servers.
Hit a paywall or forced registration after just 2 basic conversions.

So I decided to build MiniTools (https://getminitools.com) — a suite of 30+ web tools designed with a strict Zero-Server Client-Side architecture.

🔒 How it Works Under the Hood

Instead of sending your files across the internet to a backend worker, MiniTools performs every operation directly inside your browser memory:

PDF Manipulation: Merging, splitting, rotating, and compressing PDF files runs locally using pdf-lib and modern WebAssembly.
Image Optimization: Binary-search canvas compression algorithms that reduce photos to exact file size limits (e.g. strict 30KB / 50KB limits required for government and visa portals).
Fast Format Converters: HEIC to JPG, WebP to PNG/JPG, PNG to JPG without touching a server.
Business & Math Calculators: Multi-country VAT/Tax breakdown, business days counter (excluding weekends), rule of three proportions, and percentage calculators.
PWA & Offline Ready: Service worker caching ensures that once loaded, you can use these tools even on an airplane with zero internet connection.

🛠️ The Tool Suite

You can explore the full collection here: https://getminitools.com

📄 PDF Suite: Merge PDF, Compress PDF, Split PDF, Rotate PDF, PDF to Word (.docx), PDF to JPG.
🖼️ Image Suite: Image Compressor, Compress to 20KB/30KB/50KB, Circular Avatar Crop, Image Resizer, HEIC to JPG, WebP Converter.
🔢 Calculators: VAT/Tax Calculator, Working Days Calculator, Rule of Three, Percentage & Discount Calculators, Age Calculator, Currency Converter.
🛠️ Dev Utilities: Text Diff Checker, JSON Formatter, Base64 Encoder/Decoder, Unix Timestamp, Password Generator, QR Code Generator.

🌍 Multilingual & Open

The platform is fully translated and accessible in 6 languages (English, Spanish, Portuguese, French, German, and Italian).

Check out the live website: getminitools.com

GitHub repository: github.com/Mecsocse/getminitools

I’d love to hear your feedback, bug reports, and suggestions for new tools to add! 🚀

How I built a Premium ROI Calculator with Pure HTML/CSS/JS (No Frameworks)

Mecso — Mon, 13 Apr 2026 07:16:29 +0000

Working with agencies, I noticed they all have the same problem: explaining ROI to clients is hard. Most calculators out there are either ugly or require heavy plugins.

I decided to build a minimalist, high-converting ROI Calculator using only Vanilla web tech. No React, no jQuery, just clean code.

The Tech Behind It

Vanilla JS: Handles the logic for the 4 sliders (Ad Spend, CPC, Conversion, and Sale Value).
CSS Variables: To make the UI easy to customize.
Responsive Design: It works perfectly on mobile and desktop.

Why Vanilla?
Performance is key for landing pages. This widget loads instantly and doesn't bloat your site. It’s a single file you can drop into any project.

Want the source code?
I've spent hours polishing the UI and commenting the code so anyone can use it. If you want to save yourself the dev time and add this to your client sites today, you can grab the full source code here:

Get the ROI Calculator on Gumroad:
https://albertpuig.gumroad.com/l/vumuqb

I’m curious —do you use calculators on your landing pages to boost conversion? Let me know in the comments!

DEV Community: Mecso

I Built 30+ Free Web Tools with Zero Server Uploads (100% Client-Side)

🔒 How it Works Under the Hood

🛠️ The Tool Suite

🌍 Multilingual & Open

How I built a Premium ROI Calculator with Pure HTML/CSS/JS (No Frameworks)