A spa and swim spa cover lifter having a footplate with an elongated undermount that becomes secured under a spa or swim spa for added lifter stability and strength during the raising and lowering of a spa cover. The upper structure of the cover lifter is quickly and easily separated from the footplate, allowing its prompt removal for spa maintenance without the burden/expense of emptying and refilling the spa. The upper structure comprises two vertically-extending supports each having two permanently attached L-shaped brackets providing lateral sway reduction for the vertically-extending supports under load. Three fasteners removably secure each vertically-extending support and its two associated brackets to the wider/exposed end of the footplate. The bottom part of each fastener is permanently fixed to the footplate, preferably by welding. A pre-assembled body comprising adjustable spa cover support arms and lifting-assist/lowering-assist means is fixed to the vertically-extending supports using two height adjustment knobs.