These are the most famous community tools. They "trick" the FUS into thinking a device is requesting an update, allowing power users to download full firmware packages at maximum speed directly from Samsung's servers.
Sometimes a new update introduces bugs (battery drain, Bluetooth issues). By fetching an older build from the FUS server, you can downgrade. Warning: Samsung’s anti-rollback (e-fuse) may prevent downgrading if the bootloader version has changed. samsung fus server