You can hover the robot icon on the location bar and check what reason is shown in the tooltip (DevTools, Marionette, RemoteAgent). If the reason is DevTools then check on the about:config page whether these prefs have their default value (i.e. are not bold). *devtools.chrome.enabled (false) *devtools.debugger.prompt (true) *devtools.debugger.remote-enabled (false) You can check whether you have a user.js file in the profile folder to initialize prefs each time Firefox starts. The user.js file will only be present if you or other software has created this file and normally won't be present. You can check its content with a text editor (right-click: "Open with"; do not double-click). The user.js file is read each time Firefox is started and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session. You can delete the user.js file if you didn't create this file yourself. See also: *[/questions/1351089] Firefox address bar under remote control.