The successful ZX Spectrum was delivered with 16 or 48 KB of RAM as well as a cheap rubber keyboard and hardly any connectors. In the end of 1984 the Spectrum + was launched, which was delivered in a more modern case with 48 kB and an improved keyboard, but otherwise identical to its predecessor. This was followed by the Spectrum 128, which was improved technically and now had 128 kB memory. Also new were the AY-3-8912 sound chip, the serial port with MIDI compatibility, an RGB monitor port, a reset button, a larger ROM with improved BASIC and the possibility to connect an external numeric keypad. After the acquisition of Sinclair by Amstrad in 1986, the Spectrum +2 launched. It basically was a Spectrum 128 with a built-in cassette drive ("Datacorder") in a gray housing. There were also two SJ joystick ports (requiring special joysticks or an adapter to use standard Atari joysticks).

Successor was the Spectrum +3 with an built-in 3 inch floppy disk drive. Similar to the +2A (a +2 in a black case instead of grey) the +3 was not fully compatible any longer and could not run all older software titles made for the 48 and 128 range of computers. All Spectrum models sold a total of around 5 million times. The Spectrum was for a long time the best-selling home computer with the largest software offering on the British home market.