Many apps now use helpers and services to handle some of their work. Good reasons for this include needing to perform a task at a higher level of privilege, and for utilities installed into the menu bar. Background helpers can then be run as root, or provide a periodic service, split out from the main app. You manage them in System Settings, in the Login Items & Extensions part of General settings. This article looks at those set there to Open at Login, and others listed in App Background Activity. I’ll keep Extensions for another occasion.

Login Items

These are normally apps intended to be opened automatically when you log into your Mac, and most can be opened manually if you prefer. To add an app or remove it, use the + and – buttons.

To log in without any of those Login Items being started automatically, press and hold the Shift key when you click on the Log In button (at the right end of your password), and keep it held until the Dock appears. You may be asked to enter your password a second time, in which case once you have done that, press and hold the shift key again while clicking on the Log In button. Existing login items won’t then be opened until you log in again.

Background Items

Background items aren’t normally apps as such, but usually small binaries run by launchd as LaunchAgents or LaunchDaemons, in accordance with their property lists. Your control over them is limited: all you can do is turn them off and on.

If you try disabling some of them, you may see that they’re automatically re-enabled. Many appear unidentifiable, and a few have ⓘ Info buttons, to reveal where their property list is on your Mac, but many don’t. One useful piece of information given for some is whether that item affects all users, in other words is installed in a folder outside your Home folder, including the main Library and Applications folders.

Apple maintains a preference file containing details of many helpers and other executables used by major third-party apps. This may help you identify those that appear in LogIn and Background Items. This can be found at /System/Library/PrivateFrameworks/BackgroundTaskManagement.framework/Versions/A/Resources/attributions.plist

Safe mode

Diagnosing problems with helpers and services is extremely difficult, and made harder by the fact that most are now XPC services and only revealed by their entry in Activity Monitor’s lists. When they’re in trouble, they can cause almost anything, including:

• unexpected or abnormal behaviour,
• their entry in Activity Monitor can take high CPU and/or memory,
• spinning beachballs and sluggish performance,
• general instability.

The most important test to establish whether any such behaviour is likely to be the result of a third-party helper or service is to start up in Safe mode and demonstrate that the problem disappears then. This is because Safe mode blocks these helper apps and services from being launched. Unfortunately, Safe mode doesn’t help you establish the cause, nor what you should do about it.

Which Library?

In the past, most helper apps and services have been run by launchd on the basis of property lists in LaunchDaemons and LaunchAgents folders in the main Library folder, or in ~/Library/LaunchAgents. One good way to distinguish these is to create a new user account and see if the problem affects that too: if it doesn’t, then it’s more likely that helper or service is being launched from the Library folder in your Home folder rather than the main Library, in other words that the problem lies somewhere in your Home folder.

BTM dump

A better and more systematic approach is to obtain a detailed listing of all those Background Items, and uninstall or delete those you no longer need, or are just old and unnecessary. For this, you need a BTM dump, using an undocumented option to the sfltool command:
sudo sfltool dumpbtm > ~/Documents/btmdump.text
to write it to the text file btmdump.text in your Documents folder. This file is also invaluable if you’re going to nuke Login Items in a reset, as it provides a record of what you might need to restore afterwards. This uses a command tool originally intended to manage the Shared File List, which has gained additional features covering Service Management, although its man page hasn’t caught up yet and the most help you’ll get is from its usage info.

This lists full Service Management information for every item currently being managed, by user ID. Normally, the two important user IDs would be 0 for root and 501 for the primary admin user, but here the first list, with a UID of -2, appears to be a composite covering most Background Items. You should also check those for the current user, such as 501. A typical entry might be:
UUID: 9A087CA1-250D-4FA6-B00A-67086509C958
Name: Alfred 5.app
Developer Name: (null)
Team Identifier: XZZXE9SED4
Type: app (0x2)
Flags: [ ] (0)
Disposition: [enabled, allowed, not notified] (0x3)
Identifier: 2.com.runningwithcrayons.Alfred
URL: file:///Applications/Alfred%205.app/
Generation: 0
Bundle Identifier: com.runningwithcrayons.Alfred

This gives the location of the executable that is loaded. The Developer Name given is taken from the code signing certificate. The Disposition field is probably most relevant to identifying those causing problems, as it should reflect the status of that entry in the Login Items list, and whether the user has been notified. There’s currently no way to change or correct those, at least using the tools available.

BTM reset

The nuclear solution is to blow the whole lot away, and start from scratch, but if you don’t then delete old apps and their components, including property lists and support files tucked away in Application Support, LaunchAgents and LaunchDaemons folders, then many will return to haunt you. To remove all third-party Login Items and reset those and Background Items to installation defaults, you can use the undocumented command
sudo sfltool resetbtm
following which you should restart the Mac.

Summary

• Login Items are apps opened automatically when you log in, and are managed in Open at Login in Login Items & Extensions settings.
• Background Items are small binaries run by launchd as LaunchAgents or LaunchDaemons, controlled in App Background Activity.
• Hold the Shift key when clicking the Log In button to temporarily disable all Login Items.
• Safe mode disables both Login and Background Items.
• Use sudo sfltool dumpbtm to obtain a BTM dump detailing them all.
• To blow them all away, perform a BTM reset using sudo sfltool resetbtm then restarting.