Portafilter

A portafilter is the handled, removable component of an espresso machine that holds the filter basket containing ground coffee. It locks into the group head with a bayonet-style twist, forming a seal that withstands the 9 bars of brewing pressure. The portafilter is where the barista loads, distributes, and tamps the coffee dose before extracting a shot.

Portafilters come in two main styles: spouted and bottomless (also called naked). Spouted portafilters have one or two spouts on the underside that channel the espresso stream into cups, making it easy to split a double shot into two single servings. Bottomless portafilters have the bottom cut away entirely, allowing the barista to see the extraction directly from the basket — invaluable for diagnosing channeling, uneven distribution, and other technique issues.

Standard commercial portafilters measure 58mm in diameter, though some machines use 54mm, 51mm, or proprietary sizes. The filter basket inside the portafilter determines the coffee dose — single baskets hold 7 to 10 grams, double baskets hold 14 to 21 grams, and competition-style precision baskets offer exact tolerances for consistent dosing.

The material and mass of a portafilter matter for thermal stability. Heavy brass or stainless steel portafilters retain heat better than lightweight aluminum or plastic versions, helping maintain consistent brew temperature throughout the shot. Many experienced home baristas upgrade their stock portafilter basket to a precision aftermarket basket for more even extraction and improved flow.