Your Files Never Leave Your Browser.
Most online tool sites upload your PDFs and images to their servers. We don't. Every PDF conversion, image edit, calculation and generator on ToolStackTools runs 100% inside your browser — your content stays on your device.
Browse 140+ ToolsWhy this matters
- Your documents often contain sensitive data — contracts, invoices, ID scans, medical records, business reports.
- Server-based tools can store, scan or log your files — even with good intentions, that's a breach waiting to happen.
- GDPR, HIPAA and corporate security policies increasingly forbid uploading confidential files to third-party tool sites.
- Client-side processing is also faster: no upload, no waiting, no 100MB limit.
How it works
Your browser (Chrome, Safari, Firefox, Edge) is now powerful enough to do what used to require a server: parsing PDFs, resizing images, compressing files, rendering page numbers, computing mortgage payments. We use libraries like pdf-lib, pdfjs-dist and the Canvas API to run all of that locally. When you upload a file, it goes into your browser's memory — never over the network, never onto our infrastructure.
Don't trust us — verify it
Open your browser's DevTools → Network tab. Upload a PDF to Merge PDF or Compress PDF. Watch: zero upload requests. The file never leaves your device. Same applies to our Image Compressor, Resizer, Converter, PDF Watermark, Protect PDF, Unlock PDF and dozens more.
What about the AI tools?
Honest answer: AI writing tools (like AI Summarizer, Grammar Fixer, Resume Generator) do send your prompt to a secure AI gateway — that's the only way generative AI can work. We don't store your prompts, don't train on them, and don't sell them. For the 100+ non-AI tools, nothing leaves your browser — and those are marked with a 🔒 Private badge.