Z-offset

Z-offset is a small calibration value that tells the printer exactly how close the nozzle tip sits to the bed at the start of a print, correcting for the tiny real-world gap between where a sensor or manual leveling process says the bed is and where the nozzle actually makes contact. Even printers with automatic bed leveling still need this one manual adjustment.

Getting z-offset right is different from bed leveling itself: leveling makes the bed flat and even across its whole surface, while z-offset sets the overall height at which the nozzle starts printing on that leveled surface. Too far away and the first layer will not stick. Too close and the nozzle will scrape, squish filament sideways, or fail to extrude cleanly at all.

Most printers let you nudge z-offset up or down in small steps, often while watching the first layer print live, then save that value for future prints. A common mistake is changing the physical build surface, such as swapping to a thicker or thinner bed sheet, without re-checking z-offset afterward, since that changes the real gap even though the printer's saved setting has not.