Chrome historically has many meanings in Mozilla.

Browser chrome / Chrome
The "browser chrome" is the UI around the web page, as opposed to the content area.
More generally, chrome is the entirety of entities making up the user interface of a specific application or extension.
A chrome:// URL
An URL using the chrome:// protocol. Code loaded from a chrome URL has extended, or chrome, privileges.
XUL-based applications load the code for their interface from chrome:// URLs.
Chrome privileges
The code running with chrome privileges is allowed to do everything, unlike the web content, which is restricted in several ways.
chrome argument to
Passing the chrome argument to opens a new window without any browser interface elements.
chrome folder
This folder is usually a part of a XUL-based application installation. Applications usually load their UI files from the files in this folder.
-chrome command line argument
Starts the application and opens the specified XUL file in a top level window. E.g. mozilla -chrome chrome://inspector/content starts the DOM Inspector.
Chrome package
A chrome package consists of a set of chrome providers. There are three basic types of chrome providers:
  • Content. Content can consist of any file type viewable from within Mozilla. In particular, the content provider most often consists of a set of XUL, JavaScript and XBL binding files.
  • Locale. Translations for multi-language support. The two main types of files are DTD files and java-style properties files.
  • Skin. The skin provider provides complete appearance data for the user interface. Consisting of CSS files and images.
The chrome registry, stores the list of registered chrome packages and other information. It was located in the install directory and in the profile. It is no longer used since Gecko 1.8 (Firefox 1.5).

See also

(Note that while both of the documents below mention contents.rdf files, an easier way of registering your chrome providers - using Chrome Manifests - is supported since Firefox 1.5 / Toolkit 1.8)

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Last updated by: Kastor,