Mac storage basics · Browsers and everyday apps
Why do I have both a .zip file and a folder of the same name in Downloads?
Short answer: Safari (or a double-click) unzips archives but keeps the .zip, so content is stored twice. Delete the .zip once the folder opens fine; you can turn off Safari's auto-open setting.
Safari's Open "safe" files after downloading setting (in Safari → Settings → General) unzips archives for you, and other apps or a double-click do the same. The original .zip usually stays, so the same content takes space twice.
Once you've checked the folder opened correctly, delete the .zip. Turning off that Safari setting means archives stay zipped until you open them, which some people prefer for keeping Downloads tidy. Repeated downloads also create copies named with "(1)", "(2)" — those can usually go too.