The DOI Resolver browser extension does exactly what its name suggests. Often on publisher sites and institutional repository pages, Digital Object Identifiers (DOIs) are shown (such as 10.1016/S0921-4526(00)00753-5) but aren't actual links. DOI Resolver allows you to highlight the DOI, right-click, and select "Resolve DOI" to be taken directly to the item. Also, clicking on the DOI Resolver icon opens a DOI search. One useful feature is the extension's ability to generate a QR code for the DOI.