First layer

The first layer is the very first pass the nozzle makes onto the build plate, and it matters more than any other layer because every layer after it depends on it sticking down flat and even. If the first layer is too far from the bed, it will not stick at all. If it is too close, the nozzle drags and squishes filament unevenly or does not extrude cleanly.

Most print failures that look like a filament or printer problem actually trace back to first layer setup: a bed that is not level, a nozzle that is not zeroed to the correct starting height, or a build surface that is dirty or worn out. Getting this step right, whether through manual bed leveling or an automatic leveling sensor, solves the majority of adhesion complaints beginners run into.

A good first layer looks slightly flattened and shiny, with lines that touch their neighbors without gaps or obvious squishing. Common mistakes include leveling the bed cold and then printing hot, which changes the gap slightly, and giving up on a build surface after one bad print instead of checking level, cleanliness and nozzle height first.