In implementations of glyph weight modification, a glyph modification system represents an outline of an unmodified glyph as segments having start points and endpoints. The segments have directions based on the start points and the endpoints such that an endpoint of a segment is a start point of another segment. The system identifies features of the unmodified glyph based on the segment directions. A property of the unmodified glyph can be modified by changing coordinates of points of the segments based on the identified features. The glyph modification system generates a modified glyph having the modified property using the points of the segments with the changed coordinates.