It depends on the Content-Disposition header: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Disposition https://developer.mozilla.org/en-US/

It depends on the Content-Disposition header: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Disposition https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Co.... There are extensions that let you intercept this header, e.g. https://addons.mozilla.org/en-GB/firefox/addon/no-pdf-download/ https://addons.mozilla.org/en-GB/firefox/addon/no-pdf-downlo... which per https://github.com/MorbZ/no-pdf-download/blob/c924d657f33398e2a3a51a7a67608b6156a99124/app/src/headers.js https://github.com/MorbZ/no-pdf-download/blob/c924d657f33398... detects the content-type and if it’s PDFy replaces the content-disposition header with “inline”. (Clicking on a link that has the download attribute set also affects things: https://developer.mozilla.org/en-US/docs/Web/API/HTMLAnchorElement/download https://developer.mozilla.org/en-US/docs/Web/API/HTMLAnchorE....)