How to Build a Client-Side PDF to JPG Converter (No Server Required)

Most online PDF converters work the same way: you upload your file, their server processes it, and you download the result. Simple — but it means your document passes through someone else's infrastructure. For sensitive files like contracts, invoices, or ID scans, that's a real concern. In this post, I'll show you how to build a PDF to JPG converter that runs entirely in the browser using PDF.js. No server, no uploads, no backend — just JavaScript. Why Client-Side? When you process files in the browser: The file never leaves the user's device No storage costs or server infrastructure needed Works offline once the page loads Faster for the user (no upload/download round trip) The tradeoff is that client-side processing is limited by the user's device CPU and RAM. For most use cases — converting a few PDF pages to images — this is completely fine. What We'll Use PDF.js — Mozilla's open-source PDF rendering library Canvas API — built into every modern browser File API — for reading the us