Let’s See, Mac can’t delete the app because it’s open in Backgroud of Use. Are you trying to remove unwanted Apps that are installed on your Mac, But Mac System shows or gives a message like “app can’t be moved to the trash because it’s open or in Use”, “After force quiet app running the app on screen still not deleting”.
Here I found the exact solution for all the Mac users who are running any macOS. I also discussed why this happens for the selected apps that cannot delete from Launchpad or under the application folder. Becuase it stays on Top Menu Bar like Google Drive, DropBox, Skitch…after quit from the screen.
Also, a message clearly shows the app is running, open, or in use. So, first, we need to find where the app is open and how to identify it. In the reply, the activity monitor will help to find running the app in the background, then force close from the activity monitor.
Our readers mail us and ask the solution for queries like they can’t empty trash Mac because don’t have permission, file in use or facing error 8003, or some guys getting error code 50, or their time machine, can’t empty trash on Mac external hard drive. We advise all of them to follow the given solutions.
Can’t Delete App on Mac says it’s Open (Fix in 3 Steps)
Step 1: To check running the app on activity monitor, Open spotlight search (Command + Space) > type “Activity Monitor” > Search app name from the search box under the Memory tab.
Step 2: I want to delete the Fotor Photo Editor app. Select all the process threads of Fotor Photo Editor individually and click on the ‘X‘ ❌ mark in the activity monitor.

Step 3: Next, the Activity monitor will ask for the “Force Quit” process, Go with it and done by completely stop all the processes behind the particular app.
The process will be removed from Activity Monitor. If not, then try again to Force Quit

After closing down all types of process threads from the system, we can uninstall applications in alternate ways.
Move Trash or Uninstall the App from the Application Folder
Under the Application, folder, find the app you want to move into the Trash/Remove or uninstall.

Note: you can’t remove or uninstall the app that has been preinstalled on a system with MacOS. Make sure to remove only a third-party or app store app.

Above steps, we should try in the case simple method to force quit or uninstall app not work or close frozen windows on Mac.
Use Uninstaller
Can’t uninstall the app after force stop?
Still, can you uninstall the app after stopping all app processes? Now, you must use the uninstaller app for the app you installed on your Mac. Some apps keep the installer app in the Applications folder or You have to download it from the app’s official website. To find the app uninstaller on Mac,
Open finder > from the top menu Go > Applications > Utilities > Find the uninstaller for the app you are looking for. Here’s my screen,

Just like, Uninstall forticlient On Mac.
Run the Setup and Follow the on-screen instructions.
As a second option, Developers are also officially giving uninstallers for their products from the website. Check for that and Uninstall the program using the official uninstaller.
Tips on “This app can’t be moved to the trash because it’s open or in Use” really worked for you, then don’t miss to share with us on the comment, Also with your friends via the social share button.
BOOM! Was driving me nuts……..thank you for a great fix!!!!
Thank you. How can I offer you a coffee?
it’s pleasure for me! Thanks for your feedback.
Thank You so much! I had downloaded and tried pCloud. It was no good, and they have NO uninstall instructions at all, not even in their FAQ’s. pCloud won’t let you move the application to the Trash, and says it’s open. Companies that pull this nonsense, and won’t let you uninstall their garbage should be punished by the DOJ.
Thank You again for your help.
Thanks for your feedback!
Wow ! Thank You so much for this solution!
This is very helpful.
This is very helpful. Thank you 😊
WOWWW!! its done Thanks a lot