Split in three steps
- Add your PDF.
- Choose a split method, such as page ranges or every page.
- Download the new PDFs or the ZIP.
For every split option, see Split PDF.
How splitting runs in your browser
- Thumbnails. pdf.js (pdfjs-dist), Mozilla's open-source PDF renderer, reads your file in the page and draws a small picture of each page so you can see what you're selecting. Part of pdf.js runs in a helper file, the pdf.js worker. Your browser downloads it from pdfwrangle.com once, then keeps it in memory for every file.
- Building the new files. pdf-lib, an open-source JavaScript PDF library, copies the pages you chose into new PDF documents. Pages are copied as they are, not re-rendered, so text and images are unchanged.
- Zipping. When there's more than one file, fflate, a small JavaScript ZIP library, bundles them into one ZIP in memory. The PDFs are stored in the ZIP without extra compression, which keeps it fast.
- Saving. Each download comes from a blob: link, which points at your browser's memory rather than at a server.
What your browser downloads
Everything you see in the Network panel is your browser downloading something from pdfwrangle.com, not sending your file to it. When a page loads, that includes the page itself, its JavaScript files under /_next/static/, fonts, the logo, and small page-data files for the links in the menu (their names end in .txt?_rsc=…), which the site prefetches so other pages open faster. All of these are GET requests, and none carries your file.
The split tool fetches pdf.js and its worker (about 1.4 MB) the first time you open a PDF on the page, not when the page loads.
Verify it yourself
Test 1: split with the internet switched off.
- Open this page and wait until it has fully loaded.
- Open one PDF while you're still online. This makes your browser download pdf.js, which only loads when it's first needed. If you go offline before this, the PDF won't open, because the renderer was never downloaded.
- Disconnect: turn off Wi-Fi, or choose Offline in the throttling menu of DevTools > Network.
- Add another PDF (or use the same one), split it and download the result. In our test it kept working offline, and nothing was downloaded again.
Test 2: watch the Network panel.
- Open the tool page and wait until it has fully loaded.
- Open your browser's developer tools: press F12 (Windows, Linux) or Cmd+Option+I (Mac) in Chrome, Edge or Firefox, and select the Network tab.
- Clear the list (the clear button in the Network toolbar), so only new requests appear from now on.
- Add a PDF, choose how to split it, and download the result.
- Look through the new requests. To show the Method column in Chrome or Edge, right-click a column header and tick Method. An upload would show up as a POST or PUT request with a body about as large as your file. You should find none. The first time you open a PDF on the page, you'll see two JavaScript files under /_next/static/chunks/ and a file under /v/ whose name starts with pdf.worker being downloaded. That's pdf.js, which draws the page thumbnails. After that you may see blob: entries, which are the worker starting from your browser's own memory. The ZIP and the split PDFs are created in memory, and their downloads come from blob: links, not from the server.
We ran both tests on the live site in Chrome on 20 October 2026, with our own test files. While the tools worked, the browser sent no POST or PUT requests and no request with a body. The only traffic was the GET downloads described on this page.