Where can i find and clean up partially downloaded content?

Say your download of 17gb application is interrupted and can't continue since you are out of space.

Knowing the application name, where can you look to find parts of what has already been downloaded so you can remove it?

The temporary location that stores downloading files varies between computers. Here's how to find it:

1. Start a rather large app store download
2. Open Activity monitor, and select the storedownloadd process. (storeagent for 10.9 and below)
3. Open the Inspector (press the "i" button, or ⌘+i)
4. Select the Open Files and Ports tab, and scroll to the bottom
5. Select the path that starts with /private/var/folders that contains com.apple.appstore from the beginning, up to and including com.apple.appstore
6. Open Terminal and type open [paste path here] and hit return
7. From here, you can see all the temporary files the Mac App Store has made. You can get info on each one to see their sizes, and dispose of them accordingly.

Here's another way to find the Mac App Store downloads folder by enabling the debug menu:

1. Quit the App Store
2. Open Terminal
3. Run command: defaults write com.apple.appstore ShowDebugMenu -bool true
4. Open the App Store
5. Select the new "Debug" menu in the menu bar and choose "Show Download Folder..."

Demo: https://gfycat.com/KindLimpBarracuda

As of macOS 11.4, those can be found here:

/private/var/folders/[folder1]/[folder2]/C/com.apple.appstoreagent/com.apple.appstore/

where:

[folder1] and [folder2] are temporary folders

For example:

/private/var/folders/xk/s3v4txqs7v3b6rvsd6f9yjhw0000gn/C/com.apple.appstoreagent/com.apple.appstore

You can look for such folders with this command:

sudo find /private/var/folders -path '*com\.apple\.appstoreagent*' -type d -name com.apple.appstore 2>/dev/null