32BitAppCheck is an app that scans for 32-bit apps on your Mac. It can help you prepare for macOS Catalina because this release will end support for 32-bit apps. It takes about 30 seconds to scan your computer (longer if you have hard drives plugged in). Once it’s finished it will present a list of all the 32-bit apps it found, which you can save as an .RTF file.
Information then collected in the app’s window begins with a list of 32-bit applications, followed by 32-bit preference panes found in System preferences. Then, you will see 32-bit system extensions, and 32-bit system frameworks. These software will include both Apple and 3rd-party software. You can then edit the information, changing fonts, and adding notes. Click Save to save the information in an RTF file. The most recent information with you edits is also saved within the app.
You can download the app here. As this is an app outside of the Mac App Store, I scanned it for malware using VirusTotal, and it appears to be clean. For an additional resource I’ve also written about Go64, which does the same thing and the UI is a bit more friendly.