I built 50+ free browser tools that run without uploads, servers, or accounts

I spent the last few months building NexaTools — a suite of 50+ browser-based tools that do everything from converting images to generating PDFs, testing regex, and transferring files between devices.

The key constraint: most tools never send your data to a server.

Why I built this

I kept using online file converters that required uploading files to unknown servers. For sensitive documents, screenshots, or anything with metadata — that's a problem.

I wanted tools that:

Run entirely in the browser (client-side)
Work offline after first load (PWA)
Have no file size limits
Don't require accounts, sign-ups, or even JavaScript frameworks
Handle real-world tasks (not just demos)

What's in it

Media tools

Image Converter — WebP, PNG, JPG, AVIF, GIF via Canvas API
Video Converter — MP4, WebM, MKV, AVI using FFmpeg WebAssembly
Audio Converter — MP3, WAV, OGG, FLAC, AAC with bitrate control
EXIF Stripper — Remove GPS and camera metadata from photos
Background Remover — TensorFlow.js-based AI background removal

PDF tools

Merge, split, rotate, delete pages
Add watermarks and page numbers
Convert images to/from PDF
Redact sensitive text permanently

Developer tools

JSON Formatter — with syntax error diagnostics
Regex Tester — live match highlighting and capture groups
Code Formatter — JS, TS, JSON, HTML, CSS, Python
Hash Generator — MD5, SHA-1, SHA-256, bcrypt
Base64 Image Encoder/Decoder
Diff Checker, URL Encoder, Markdown Editor

Utility tools

P2P File Transfer — WebRTC peer-to-peer, no server relay
Scientific/Graphing Calculator
Currency Converter — 150+ currencies, live rates
QR Code Generator/Scanner
Password Generator — cryptographically secure
Word Counter, Pomodoro Timer, Age Calculator
Microsoft Store Link Generator
APK Side Loader
URL Shortener

Technical approach

The stack is simple:

Frontend: Vanilla HTML/CSS/JS + React for the main app shell
Media processing: FFmpeg compiled to WebAssembly (runs in browser)
File transfer: WebRTC with a lightweight signaling server
PDF manipulation: Client-side libraries
Backend: Node.js + Express for URL shortener, file transfer signaling, and donations only

The interesting part is how FFmpeg WebAssembly works. The entire FFmpeg binary (~25MB) loads into the browser's memory and processes video/audio locally. This means:

No upload/download cycle for conversion
Works on files larger than what most free converters allow
No server costs (beyond hosting the static frontend)

For file transfer, I used WebRTC to establish direct browser-to-browser connections. The signaling server only helps devices find each other — the actual data transfer happens peer-to-peer.

What I learned

WebAssembly is production-ready. FFmpeg WASM handles real files without crashing.
PWA caching is tricky. You need careful cache invalidation for updated tool logic.
Privacy-first is a real differentiator. Users actually care about where their files go.
Simple tools win. The word counter and QR generator get more usage than the fancy stuff.