An ink cartridge, also known as an inkjet cartridge, is a component of an inkjet printer that contains the ink that is deposited onto paper during printing. Each ink cartridge contains one or more ink reservoirs, and certain producers also add electronic contacts. Most consumer inkjet printers use a thermal inkjet, where inside each partition of the ink reservoir is a heating element with a tiny metal plate or resistor. In response to a signal given by the printer, a tiny current flows through the metal or resistor making it warm, and the ink in contact with the heated resistor is vaporized into a tiny steam bubble inside the nozzle. This bubble then propels a droplet of ink onto the paper, creating the printed image.

Ink cartridges can contain either pigment-based or dye-based ink, depending on the cartridge series. Dye-based ink is more common and is great for producing vibrant color prints and photos, but it is not waterproof and can be susceptible to smudging. Pigment-based ink lacks the brightness of dye-based ink but offers a crisper finish and dry time. Pigment ink can resist fading for up to 200 years and is appreciated for its ability to print archival quality images.

Some printer manufacturers set up their cartridges to interact with the printer, preventing operation when the ink level is low or when the cartridge has been refilled. However, some researchers have found ways to override such interlocked systems and print up to 38% more good quality pages after the chip stated that the cartridge was empty.

Ink cartridges can be expensive, and in some cases, cartridges can cost more than the price of the printer itself. Some cartridges have a sealed design, and most of them don’t support refilling. Inkjet cartridges thick ink can dry after months, making them useless, which can make using an inkjet printer comparatively expensive if unused.

Ink tank printers are refillable ink printers with an inbuilt printhead. These printers use ink tanks that can be topped up as needed from an ink bottle and are supplied directly to the printer via an integrated ink system. Printers with ink tanks tend to be referred to as ‘continuous ink tank printers’ .