I built a multi-language privacy-first online tool suite, everything runs locally inside your browser

#nextjs #showdev #sideprojects #webdev

I built a multi-language privacy-first online tool suite, everything runs locally inside your browser

If you’ve used random free online tools recently, you’ve probably run into the same frustrations:

You have to register an account just for a one-time quick task
Annoying ads and forced watermarks on your exported files
You upload private photos, PDFs or text data to unknown third-party servers
Many tools only support English, no multi-language interface

That’s why I spent months building Korelyy Tools, a collection of everyday web utilities with a simple core rule:
All processing happens locally in your browser. Your files never leave your device.

What’s inside the toolkit

Right now the site includes common utilities for regular users and developers:

Image compression & conversion
QR Code generator & reader
PDF basic tools
Emoji mixer
JSON formatter / validator
AI text writing helper
More dev-focused small utilities on the roadmap

Core design choices I stuck to

✅ No signup, no login required for any tool
✅ Zero watermarks on all outputs
✅ Client-side computation: No file uploads to backend servers
✅ Multi-language support: English, Chinese, Spanish, French, Hindi, Arabic
✅ Static site built on Next.js, low long-term hosting costs

Technical challenges I ran into

Building fully client-side tools wasn’t as straightforward as I expected:

Browser memory limits
Large images and multi-page PDFs can easily trigger tab crashes. I added chunk processing to avoid out-of-memory errors.
Web Worker performance
Heavy tasks block the main thread, so I moved compression and document parsing into Web Workers to keep the UI responsive.
Multi-language i18n management
Maintaining translation strings for six languages adds a lot of repetitive work. I’m still optimizing how I manage localization files.
SEO for dozens of independent tool pages
Each small tool needs its own meta title, description and structured content to rank on search engines. It’s a slow ongoing process.

Current status & growth

After launching publicly, the site hit around 1.2k pageviews in the first 28 days with zero paid ads. Most traffic comes from organic search at the moment.

There’s still a long feature list I want to implement: