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

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

What's next

• More blog posts explaining the privacy model
• Adding offline support to the URL shortener
• Community-contributed tools
• Open-sourcing the WebAssembly build pipeline

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Try it: nexatools.in — free, no accounts, works offline.

I'd love feedback on the tools or the technical implementation. What browser-based tools do you wish existed?