Mask writers have evolved significantly in the last decade, and many modern ones include some level of process error correction. However, the feature sizes were shrinking at even faster rate, so the ratio of error to feature size has grown to a level that can no longer be ignored. Even “ideal” process will still produce some rounded contours on the mask. This paper discusses potential applications for the mask contour approximation, such as manufacturing rule check, inspection, metrology and mask error correction. We also discuss and compare possible approaches to generate the mask contours.