A tamp, or tamper, is used during the preperation of a shot of espresso to compress ground coffee into a puck, within the portafilter's basket. Tamps vary in weight, diameter, and design; generally, the diameter should match that of the basket, and the weight is a personal preference.

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To tamp is the action of tamping the coffee into the basket. This is a small art-form in itself, with espresso fanatics going to great lengths to achieve the perfect puck, and prevent the pitfall of uneven extraction that occurs with uneven compression of the coffee. It is not unusual for the tamping process to involve several steps, including compression with different tamps, at different pressures. A small set of scales is useful to quantify the pressure used for each tamp.

Increasing the tamping pressure will increase the brew time of a shot of espresso, and thus increase the extraction from the coffee, resulting in a stronger shot.