There are fan-made "GTA 5" clones or mobile ports adapted for low-end PCs that may have a download size around 1GB. These are not the official game and usually expand to roughly 2GB after extraction.
If you download a file claiming to be GTA 5 compressed to 1GB, you are likely encountering one of three scenarios:
Some scammers repackage the old fake APK or a 2013 demo tech demo and rename it “PC Full Version.”
You may download a 1GB file that only contains audio folders or empty data, proving to be 100% fake.