Firefox uses the "chrome://" protocol to access its internal files and other elements (parts of the window that don't belong to a website). This has nothing to do with Google Chrome, we started using this protocol long before that browser came out.

https://developer.mozilla.org/en-US/docs/Glossary/Chrome <blockquote>In a browser, the chrome is any visible aspect of a browser aside from the webpages themselves (e.g., toolbars, menu bar, tabs). This is not to be confused with the Google Chrome browser.</blockquote> The web browser we know as Firefox started out as Phoenix originally starting 0.1 (to 0.5) was released September 23, 2002, which was six years before the Google Chrome web browser was released at 1.0 back on December 11, 2008. These are old articles however they list several different chrome:// urls used or used to be used in Firefox. http://kb.mozillazine.org/Chrome_URLs http://kb.mozillazine.org/Dev_:_Firefox_Chrome_URLs A mention of chrome does not mean it is part of Google Chrome. Just like the Java Plugin has nothing to do with JavaScript in Firefox even though it has Java in the name as JavaScript was originally going to be called LiveScript. There is also the userChrome.css and userContent.css that you put in chrome folder and of course has nothing to do with Google Chrome. http://kb.mozillazine.org/userChrome.css http://kb.mozillazine.org/userContent.css