Merge PDFs in Your Browser: Why I Didn't Use a Server

Every PDF merger online either has a file size limit, requires uploading to a server, charges $10/month, or slaps a watermark on your output. I was sick of it, so I built my own.

The Pain Point

Last year I needed to merge 15 PDFs for a client’s proposal. The “free” tools capped me at 5 files. The premium tools wanted a subscription. And every single one required uploading my client’s confidential documents to some server I didn’t control.

So I built a PDF merger that works entirely in your browser.

How It Works

Under the hood it uses pdf-lib, a JavaScript library compiled to WebAssembly. It reads PDFs directly from your file system using the browser’s File API, merges them page by page, and downloads the result — all without a single HTTP request to a server.

The Benefits

Privacy first. Your files never leave your computer. No uploads, no server-side storage, no data leaks. For client work with NDAs and sensitive information, this is non-negotiable.

No file size limits. The only constraint is your browser’s memory. I’ve merged 500MB+ PDFs without issues. Good luck finding a “free” online tool that lets you do that.

Drag, reorder, merge. You can drag-and-drop files to reorder them before merging. The interface is instant because there’s no network latency — everything happens locally.

Costs nothing to run. There’s no server to maintain, no API key to renew, no usage limits. It’s just static HTML and JavaScript.

Give it a try at /pdf-merger. Your files stay on your machine, I promise.