How to identify 32bit applications on macOS without running each one?
System Information uses the Spotlight index to find all applications accessible on the system.


Open the app (/Applications/Utilities/System Information.app
or Apple menu → About This Mac → System Report…).
Choose Applications under Software in the sidebar and wait for the data to load.
One of the columns present on this list is ‘64-Bit (Intel)’. 

Clicking on the column header sorts the column by the Yes/No values within.
Inspecting the apps listed as ‘No’ will tell you which apps are not 32-bit.




You can also use Spotlight's CLI tool, ‘mdfind’ (/usr/bin/mdfind) on the command line. Run the following in Terminal:

mdfind "kMDItemExecutableArchitectures == '*i386*' &amp;&amp;
  kMDItemExecutableArchitectures != '*x86*'"


which returns paths to the application, such as:

/Applications/KeyBindingsEditor.app
/Applications/Impactor.app
/Applications/DVD Player.app
/Applications/Tuxera Disk Manager.app
/Applications/LICEcap.app
/Applications/Utilities/Adobe Flash Player Install Manager.app
/Applications/Compressor.app
/Applications/JPEGmini Pro.app


Currently in macOS 10.13, the following Apple first-party apps are 32-bit and still need updating or removing in 10.14:


/Applications/DVD Player.app
(probably being removed)
/System/Library/Input Methods/InkServer.app
(for the Ink support i.e. graphics tablets, probably being removed)
/System/Library/Frameworks/QuickLook.framework/Versions/A/Resources/quicklookd32.app
(a 64-bit version already exists, quicklookd.app without the 32 in the name)