Menu extras in OS X are small menu bar additions that appear on the far right of the system menu; they include a number of built-in controls such as the volume, Wi-Fi, and date and time menus. Third-party developers can also create their own menu extras. I've written about managing menu bar additions before -- usually you can just hold the Command key and drag the menu extra off the menu bar to remove it. But sometimes, depending on the development method used to create it, the menu extra won't allow you to disable or delete it.
These stubborn menu extras are usually located to the left of the built-in ones, as they are governed by a process other than the SystemUIServer, which is responsible for managing Apple's built-in menu extras. Therefore the system loads them after the built-in menus.
If you find such menu extras on your system and wish to do something about them, there are several ways to do so. But first you have to figure out what's causing the problem.
One possibility is that the menu extras could be part of an out-of-date application package that you are no longer using. Sometimes menu extras are stored within the program and are launched at start by a helper tool. This tool, a link to it, or a daemon/agent script to launch it, can be in the following locations:
- User log-in items -- managed in the Users & Groups system preferences.
- System Startup items -- located in the /Library/StartupItems folder (this is rarely used)
- User or system Launch Agent folders -- located in the user and global library folders, is a common method for keeping programs running in OS X (see here for more information on launch agent folders).
In most cases simply removing the program and any enclosed helper tools should be enough to remove the menu extras and prevent them from loading, but in other situations this may not be the case.
Menu extras and other similar system modifications can also be implemented using a plug-in unit called a bundle, which is stored in the global or user library folders in the following locations, the first being a global location that affects all user accounts, and the second being specific to the account specified by "username":
Bundles in these directories are similar to applications, kernel extensions, and application plug-ins, in that they are hierarchically structured with specific instructions on how their contents are to be used. The exception is that though applications need to be launched directly by a user, kernel extensions are loaded by the kernel, and plug-ins are loaded by their respective applications, bundles are loaded at runtime (when the system loads or when the user logs in) and provide a global service for the user account. In a sense they are like plug-ins for your account.
These bundles have been used by many developers to add systemwide access to services for supporting peripheral devices, and adding functionality to all user accounts, including the management of various menu extras at startup and log-in. Therefore, if you have a stubborn menu extra or any other similar feature addition that you cannot seem to remove, try looking in these folders for an associated plug-in or directory that may contain a plug-in, and remove it.
A last potential offender that uses a similar approach is a plug-in manager called SIMBL, which is a scripting additions framework for AppleScript that is a launch platform for a number of custom plug-ins. While useful for applications that support it, SIMBL implements a degree of separation for plug-ins that at times makes it difficult to identify as the root cause of odd behaviors such as the launch of menu extras or toolbar additions to a program. SIMBL itself will be located in the /Library/ScriptingAdditions/ and can be removed from there, but its plug-ins will be located in one of the following two directories:
Locating and removing these components of the SIMBL installation, or at least third-party plug-ins related to the menu extra in question, should clear any problem you have with a rogue menu extra on your system.