Mac storage basics · iPhone and iPad backups and updates
What are iPhone software update files on my Mac, and can I delete them?
Short answer: They're .ipsw software files your Mac downloaded to update or restore a device. They're safe to delete; Finder downloads a fresh copy if needed.
When you update or restore an iPhone or iPad through Finder, your Mac downloads the device's software (an .ipsw file) and may keep it afterwards. These files are several gigabytes each and are only needed again for another restore of that same software.
You can delete them; Storage settings' iOS Files section lists them alongside backups. Finder will download a fresh copy if it ever needs one.