Starting on April 12, 2018 macOS 10.13.4 will start alerting you when you open a 32-bit application. The purpose of this alert is to have people contact the company or programmer who wrote the App to have them update their program. macOS 10.13 High Sierra is the last version of macOS that will run 32-bit applications without compromise.
The goal is to have all applications be 64-bit for the next version of the macOS to be released.
Apple’s article on this alert – https://support.apple.com/en-us/HT208436
How do I find the 32-bit apps on my Mac?
If you are wondering what 32-bit applications you have on your Mac you can use the Mac Check 32bit application I have written. It will provide you with a web based report of all 32-bit software that is detected on your Mac.
This application is provided as is, I do not guarantee that it is free from defects. Use this application at your own risk. I make no warranty as to the performance or ability of the application whether it is expressed or implied. Under no circumstance shall Michael Spice be liable for direct, indirect, incidental, or consequential damages resulting from the use, misuse, or inability to use this application.