LaunchAgent

LaunchAgent is a configuration entity used by the macOS service management system, launchd, to describe a job that should be started, kept alive, or monitored. A LaunchAgent is implemented as a property list (plist) file that specifies the program to run, how it is invoked, and its scheduling or persistence requirements. LaunchAgents differ from LaunchDaemons in scope and privileges: LaunchAgents run in a user context, while LaunchDaemons run with elevated privileges at system startup or during boot.

LaunchAgents can be placed in user or system locations. Per-user agents are typically stored in the user's Library folder (for example, ~/Library/LaunchAgents), while system-wide agents reside in /Library/LaunchAgents or /System/Library/LaunchAgents. LaunchDaemons, by contrast, are kept in /Library/LaunchDaemons or /System/Library/LaunchDaemons. When a user logs in, the corresponding LaunchAgent is loaded by launchd into the user session; LaunchDaemons are loaded by launchd at system startup.

A LaunchAgent plist includes keys that define its behavior. The Label key provides a unique identifier. The Program or ProgramArguments keys specify the executable and its arguments. Optional keys control timing and lifecycle, such as RunAtLoad (start when loaded), KeepAlive (whether to restart the job), StartInterval or StartCalendarInterval (scheduling), and UserName or GroupName (execution context). StandardOutPath and StandardErrorPath can redirect output.

Management of LaunchAgents uses the launchctl command. Administrators or users can load, unload, enable, or disable agents. In modern macOS, commands may target specific domains (such as gui/UserID) or employ bootstrap methods to bring agents into the running context. LaunchAgents are commonly used for background tasks, periodic maintenance, or launching user-level applications at login.