Verify the install
Check the app.
For a downloaded DMG, eject the mounted image and confirm the installed app opens from Applications. Keep the image while investigating an incomplete install.

For developers using a Mac
SDK downloads, DMG installers, and repeat files can collect between projects. Trayage helps you review what is in Downloads and choose what you still need.
Review files free · 7-day cleanup trial
US$9.99 once. No subscription or automatic trial charge.

A closer look
Trayage can flag a disk image when a similarly named app exists in Applications. That does not verify the installed version or prove the installer is no longer needed.
Trayage reviews files locally and explains why suggestions stand out. Select files and confirm before they move to Trash; Trayage never empties it.
Read the guide to DMG files38 seconds · Trayage 1.1 · Sample files · No sound needed
Good to know
Often, once the installed app works without the mounted disk image and you no longer need the installer. Keep it if you need the version offline, cannot obtain it again, or have not verified the installation.
No. Trayage reviews files directly inside Downloads or another selected folder. It is not a whole-disk cleaner, package manager, or developer cache cleaner.
No. Trayage 1.1 can compare likely duplicate contents locally, but matching files may be needed in different locations. Earlier versions may use names and sizes without content comparison. Review each copy before cleanup.
File review is free. Try cleanup for 7 days with no automatic charge. See editions and purchase details.
Review installers and possible repeat downloads on your Mac. You stay in control.