Turning PDF pages into images: what to choose and why
A PDF is a container built for printing and reading, not for editing or embedding. Sooner or later you need one of its pages as a plain picture — to drop into a slide deck, attach to a support ticket, post to a marketplace listing, or send to someone whose phone stubbornly refuses to preview documents. This page rasterises each page into a JPG or PNG on your own device, and the guide below covers the two settings that actually change the outcome.
Resolution is the setting that matters
A PDF page has no pixels. It is a set of drawing instructions — vectors, text and embedded images — that get painted at whatever size you ask for. That is why you choose a DPI rather than a pixel dimension. At 72 DPI an A4 page becomes roughly 595×842 pixels: fine for a thumbnail or a quick preview, too soft to read small print. At 150 DPI you get about 1240×1754, which is the sweet spot for screen reading and most uploads. At 300 DPI you get around 2480×3508, which is genuine print quality and also four times the memory of the 150 DPI version — on a phone, a long document at 300 DPI is the fastest way to make the tab crash.
PNG or JPG for a document page?
For pages that are mostly text, tables, diagrams or line art, choose PNG. Its lossless compression keeps letter edges crisp, and it happens to compress flat white backgrounds extremely well — a text page as PNG is often smaller than the same page as JPG. For pages that are mostly photographs, such as a scanned magazine or a product catalogue, JPG wins clearly, often by a factor of five.
A picture of a page is not the page
It is worth being explicit about what you lose. The moment a page becomes an image, its text stops being text: you can no longer search it, select it, copy a phone number out of it, or let a screen reader read it aloud. Links stop working and the file usually grows. Convert to images when the goal is showing the page — in a presentation, a thumbnail, a chat message. Keep the PDF when the goal is reading, archiving or sending a document someone may need to search.
This also explains a common misunderstanding: converting to images does not extract the photos that were placed inside the document. Each output is a flat picture of the whole page, background and text included. If you need the original embedded image on its own, you need an extraction tool, not a rasteriser.
Why it runs in your browser
PDFs are the format people use for exactly the documents they should be most careful with: contracts, payslips, bank statements, medical reports, identity papers. Uploading those to an anonymous converter means handing a copy to a server you know nothing about. Here the rendering is done by PDF.js — the same open-source engine Firefox uses to display PDFs — running inside this page. Your file is read into memory and drawn locally; the only network request is for the library itself.