The webapp runtime for Firefox, which comprises: the stub executable launcher (i.e. the binary and related files that Firefox creates for each webapp you install to your local computer) and the XUL shell (i.e. the XULRunner application that the launcher uses to load a webapp and provide it with native integration APIs). Note: bugs about Gecko's navigator.mozApps DOM API (i.e. the API that web pages use to request webapp installation) go in Core / DOM: Apps; bugs about Firefox's webapp installer (i.e. the feature that creates a launcher when the user approves an installation request) go in Firefox / Web Apps.