What is pdf.js?

PDF.js is an open-source library created by Mozilla that lets web browsers display PDF files using only JavaScript and standard web technologies, no plugins, no Adobe Reader, no extra software required. PDF stands for Portable Document Format, a file format commonly used for sharing documents that look the same on any device. The way it works is by parsing the raw bytes of a PDF file entirely inside the browser. PDF.js reads the file structure, interprets text, fonts, images, and vector graphics, then renders them onto an HTML5 Canvas element, essentially drawing the page on screen the same way a game might draw graphics. Because PDF rendering can be slow and complex, the library splits its work across two scripts: pdf.js handles the display layer you see, while pdf.worker.js runs the heavy parsing work in a background thread so the main page stays responsive. You would use PDF.js whenever you want to embed PDF viewing directly into a website or web application without forcing users to download files or rely on browser plug-ins. It powers the built-in PDF viewer in Firefox and is available as a Chrome extension. Developers can also integrate it into their own applications using the pdfjs-dist package from npm, the standard JavaScript package registry. PDF.js is particularly useful for document management platforms, online editors, and any web app that needs to show PDFs inline, from contract signing tools to digital libraries. The tech stack is pure JavaScript, with Node.js and the Gulp build tool used to bundle and compile the source files for production. No server-side component is required, everything runs inside the user's browser.