Because modern Firefox versions (v57+ or "Quantum") use the WebExtensions API, this older .xpi file is primarily compatible with or older "legacy" versions of Firefox.
JSPrintSetup-0.9.5.5.xpi is a legacy Mozilla Firefox extension designed to give web developers granular control over the client-side printing process using JavaScript. jsprintsetup-0.9.5.5.xpi
The extension worked by lowering the drawbridge. It utilized , a deprecated technology that allowed JavaScript to call native C++ components within Firefox. Because modern Firefox versions (v57+ or "Quantum") use