Mac storage basics · Finding big files, Downloads and the Trash
Can I delete .iso and .img files on my Mac?
Short answer: Usually yes — they're disk images, often OS installers, and aren't needed once installed. Keep or archive one only if you'll reinstall, and check no virtual machine still uses it.
Usually, yes. .iso and .img files are disk images — typically installers for an operating system, or a virtual machine's install media. Once you've installed what they contained, they aren't needed to run it.
Keep one only if you expect to reinstall and it's hard to download again; otherwise delete it or move it to an external drive. Don't delete an image a virtual machine is still using as its disk — check the VM's settings first. More on disk images: disk images and sparse bundles.