This section describes the functions defined in the Launch Services API.
macOS Launch Services is an API that enables a running application to open other applications or their document files in a way similar to the Finder or the Dock. Using Launch Services, an application can perform such tasks as:
Open (launch or activate) another application
Open a document or a URL (uniform resource locator) in another application
Identify the preferred application for opening a given document or URL
Register information about the kinds of document files and URLs an application is capable of opening
Obtain appropriate information for displaying a file or URL on the screen, such as its icon, display name, and kind string
Maintain and update the contents of the Recent Items menu
Although most of these services are normally performed by the Finder, other applications may also find them useful for purposes such as opening email attachments, following URLs embedded in a document, running helper applications, or opening embedded document components that were created by another application or require it for viewing or editing.
Many of Launch Services’ capabilities were formerly provided by the Desktop Manager. With the advent of Mac app bundles, however, the Desktop Manager has lost its usefulness, since it is not knowledgeable about bundled applications and simply ignores them. Similarly, Launch Services’ facilities for dealing with URLs were formerly implemented through the Internet Config API. Launch Services replaces and supersedes the Desktop Manager and Internet Config with a new API providing similar functionality, but designed to operate properly in the macOS environment.
Launch Services was created specifically to avoid the common need for applications to ask the Finder to open an application, document, or URL for them. In the past, opening such items in a way similar to the Finder required knowledge of several APIs, including the Desktop Manager, File Manager, Translation Manager, Internet Config, Process Manager, and Apple Event Manager. The Finder also had implicit knowledge of the desktop database and other information not available elsewhere for determining the correct application with which to open a given document.
Launch Services removes this specialized knowledge from the Finder and isolates it in a single, straightforward API available to any application. The macOS Finder itself uses Launch Services to open applications, documents, and URLs at the user’s request. Since the Finder does no additional processing beyond calling Launch Services, any client using Launch Services for these purposes is guaranteed to behave identically to the Finder itself.
Before reading this document, you should be familiar with the related document, Launch Services Programming Guide, which presents a conceptual overview of Launch Services and its operations.