Snapping

As of version 3 of QGIS, how snapping is carried out has changed. Snapping is a specified distance (tolerance) within which vertices of one feature will automatically align with vertices of another feature. Once enabled, users can set which layers are to be used to snap against; if vertex, vertex and segments, or just segments, are to be snapped against; and the distance from which snapping will occur. Additional topological and tracing functions have been added to further enhance the snapping toolset: