Firefox PDF Viewer from Mozilla based on JavaScript and HTML5 renders PDFs securely in the browser, and is similar to PDF Viewer offered in Chrome. Here you need to remember the fact that Chrome PDF Viewer is still a plugin built by Chrome based on Pepper API, its been offered in Sandbox by Google. Plugin based PDF Viewers in browsers always susceptible to attacks where native PDF Viewer in Firefox won’t because its not a plugin.

Firefox PDF Viewer vs. Chrome PDF Viewer

Firefox PDF Viewer renders PDFs like a web pages, so you see faster loading PDFs where it utilizes only few resources. And here necessity to use third-party plugins in browser that consume more resources is avoided.

Security: Third-party PDF plugins always pose security risks that’s why native PDF Viewer offered by Mozilla which uses pure JavaScript code is safe to use when compared to Chrome PDF Viewer.

Both PDF Viewers of Chrome and Firefox were enabled by default in browsers. That’s why when you try to open a PDF via a link in web page in both of these browsers PDF Viewers will take over third-party PDF plugins. That can be annoying, but this can be easily solved by disabling Firefox PDF Viewer and Chrome PDF Viewer so that third-party desktop PDF Reader’s plugins installed can load PDFs inline in browser.