To reduce the size of icons in Launchpad on Mac, use Terminal to change the number of grid columns and rows. Increasing the grid size makes the icons smaller. Use the commands defaults write com.apple.dock springboard-columns -int X (columns) and springboard-rows -int Y (rows), then restart the Dock with killall Dock.

Step-by-step instructions:

1. Open Terminal: Find it using Spotlight (Cmd + Space) or in the Applications folder > "Utilities."
2. Change the number of columns (for example, to 8 or 10):
   defaults write com.apple.dock springboard-columns -int 10
3. Change the number of rows (for example, to 6 or 7):
   defaults write com.apple.dock springboard-rows -int 6
4. Apply Changes: Enter the command to restart Launchpad:
   killall Dock

To return to default settings, use the commands:

defaults delete com.apple.dock springboard-rows
defaults delete com.apple.dock springboard-columns
defaults write com.apple.dock ResetLaunchPad -bool TRUE
killall Dock

This method allows you to compactly fit more apps on one screen.