This printer type used impact of pins against a ribbon to produce images of letters (and graphics) on paper. The pins are mounted in a printhead in the form of a matrix and, when pushed out onto the ribbon, produced dots on the paper. Using various combinations of pins, letters and other characters could be formed; thus the name dot-matrix.

Like impact printers in general, dot-matrix printers tend to be noisy and the ribbon needs to be changed often in order to keep the output looking as good as it can. Because the letters are formed by dots, depending on the speed of the printer, the letters output can be difficult to read (but output fast) or almost letter quality (but output slow). Some printers have a near-letter quality (NLQ) mode which uses multiple passes to fill in the blanks left by one pass.

Because of their flexibility in producing characters, a dot-matrix printer can output many different fonts in many different sizes just by changing the commands sent to the pins. These printers can even output graphics in varying quality.

There is not defined standard for dot matrix output commands from the computer to the printer so dot-matrix printers often require their own printer driver to work properly (though the default Epson command set is used by many dot-matrix printers and so will often drive even non-Epson printers).