There are two main technologies used for ink-jet printers: continuous ink-jet technology and random ink-jet technology. The early ink-jet printers and the current large format ink-jet printers all use continuous ink-jet technology, while the current popular ink-jet printers generally use random ink-jet technology. Continuous ink-jet technology is represented by charge modulation. In random ink-jet system, ink is sprayed only when printing is required, so it is also called on-demand.

When inkjet printers print images, they need to carry out a series of complicated procedures. When the printer nozzle quickly sweeps the print paper, the innumerable nozzles on it will spray innumerable small ink droplets, thus forming the pixels in the image. There are generally 48 or more independent nozzles on the printer head to spray ink of different colors.