How ToolK.io works

ToolK.io ships 87 tools that process your files entirely in your browser. Nothing uploads to a server, no account is required, and there is no premium tier. This page explains how that's technically possible and which open-source libraries make it work.

The three pillars

🔒

Files never leave your browser

Every transformation — PDF merge, image conversion, OCR, video trim, encryption — runs locally with WebAssembly. We never see, store, or proxy your files. The only network traffic is the page assets themselves.

⚡

Zero servers for processing

ToolK.io has no backend for the tools. The site is statically rendered (Next.js + Vercel CDN), and the heavy lifting happens in your tab via WASM. Three of the 87 tools (PDF unlock, weather, gas prices) hit a tiny Node API for tasks that can't run client-side; everything else is 100% local.

🌍

30 languages, 0 sign-ups

Every tool, blog post and tutorial is available in 30 languages. There's no free tier vs paid tier — the entire site is free and ad-supported by minimal, non-tracking ads. No usage caps, no watermarks, no daily quota.

Open-source libraries powering each tool family

We don't build cryptography, OCR, or video processing from scratch — we glue together battle-tested open-source libraries and ship them as polished tools.

pdf-libPDF read/write/edit (merge, split, watermark, page ops)

pdf.js (Mozilla)PDF rendering (preview, text extraction, highlight)

muhammaraPDF encryption / unlock (server-side, since browser crypto can't decrypt PDFs)

tesseract.jsOCR for pdf-ocr — runs entirely in your browser via WASM

@ffmpeg/ffmpegVideo trimming and conversion via FFmpeg compiled to WASM (~30 MB on first use, cached forever)

onnxruntime-webAI background removal (image-bg-remover) using a 5 MB U²-Net-Light ONNX model

umya-spreadsheet (Rust → WASM)Native xlsx engine for spreadsheet-editor — full round-trip with charts, formulas, conditional formatting

Web Crypto APIAES-256-GCM encryption (encryption-tool), SHA-256 hashing, PBKDF2 key derivation

@imgly/background-removalBackup model for image-bg-remover when the lighter model isn't a good fit

marked + DOMPurifyMarkdown rendering with strict HTML sanitisation

chart.jsChart generation (chart-gen) — exported as PNG via canvas, never uploaded

exifrEXIF metadata reading (exif-viewer, exif-remover)

What happens when you open a tool

You open a tool URL — the page is statically pre-rendered, no server compute required.
JavaScript loads only the libraries that tool needs (each tool is a separate bundle, lazy-loaded).
You drop a file → it's read into a JavaScript ArrayBuffer in your browser memory.
The relevant WASM library transforms it (in your tab, on your CPU).
The result downloads directly from your browser as a Blob — no upload, no round-trip.
Your file stays in tab memory until you close the tab. We have no record it ever existed.

How this differs from cloud-based competitors

SmallPDF, iLovePDF, Adobe Online and similar SaaS tools all upload your files to their servers. That gives them control of pricing tiers, but means your files transit through (and are temporarily stored on) their infrastructure. ToolK.io takes the opposite approach.

	ToolK.io	Cloud SaaS
File upload	Never	Required
Sign-up	Never	Required for most features
File size limit	Limited only by your browser memory (~2 GB)	10–100 MB on free plans
Daily usage cap	None	2–5 operations/day on free tiers
Watermarks on output	Never	Common on free plans
Languages	30	5–15
Works offline	Yes (after first visit, via Service Worker)	No
Source code visibility	Static JS bundles inspectable in DevTools	Server-side, opaque

Things we deliberately don't do

We don't sell, share or syndicate your data — we don't have it to sell.
We don't have 'partner' marketing pixels embedded in our pages.
We don't fingerprint your browser to build a behavioural profile.
We don't email you. There's no 'create account' anywhere — there's nothing to create.
We don't gate features behind a paywall. Every tool, every option, free forever.
We don't run cryptocurrency miners, lock features behind ad views, or push 'premium' upsells.

Try it

The fastest way to verify any of this is to open a tool, drop a file, and watch your browser's Network tab in DevTools. You'll see no upload — only the page assets.