Method and apparatus for lithographic process performance determination

A method and apparatus for determining a performance of a lithographic patterning process, the apparatus or method configured for or comprising: receiving an image of a portion of a substrate, the portion of the substrate comprising a first region comprising a first feature associated with a first lithographic exposure of the substrate at a first time, and a second region comprising a second feature associated with a second lithographic exposure of the substrate at a second time, wherein the first and second regions do not overlap and wherein the first feature and the second feature form a single feature extending along at least part of the first region and at least part of the second region; and determining the performance of the lithographic patterning process based on a feature characteristic of the first and/or second exposed feature associated with a boundary between the first region and the second region.