Or you can check the running programs in Activity Monitor and close all of them.

If the file is open or in use by an app or the system, you need to close or force quit it from the Dock.

If you insist on deleting the files that can't be deleted on your Mac, you need to fix the issue in the warning first.

Unexpectedly, when you try to delete a certain file, a warning message appears to alert you can't do that and the corresponding reasons. How do you delete files on Mac that won't delete? Now, the target files are completely removed from your Mac and won't be recoverable unless using data recovery software. And clean up download history in browsers for through downloads deletion on Mac. What is easy to overlook is that you also need to clear caches on your Mac for complete app deletion. Select the Delete Immediately option and click Delete on the pop-up confirmation window. Meanwhile, hold down the Option key, you'll find the Move to Trash option in the File drop-down menu converted to Delete Immediately. Then, navigate to the top Finder menu and click File. Open Finder and select the target file.

Select the file and hold down the Option + Command + Delete keys on your keyboard.If so, you can clear them up thoroughly from your Mac using one of the following two ways. Maybe you decide to completely delete some files without moving them to the Trash first. If you want to completely delete the files from your MacBook Pro (Files can't get back anymore), you need to right-click the Trash on the Dock and select Empty Trash after you've moved the files to there.

The quick deletion only moves your files to the Trash.

How to clear macbook air hard drive