Buffer — Tool (QGIS)

In QGIS: Processing Toolbox › Vector geometry › Buffer (native:buffer); menu: Vector › Geoprocessing Tools › Buffer.

Realises:

• Dilation — with a positive Distance
• Erosion — with a negative Distance
• Dissolve — with Dissolve result ticked
• Explode — with Keep disjoint results separate ticked as well (QGIS 4.2; not in older releases)

Settings that matter

• Distance is in the layer’s units: metres in EPSG:25832, but degrees if the layer is in EPSG:4326. Reproject first.
• End cap style Flat stops a buffered line at its ends; Round (default) adds half circles.
• Segments sets how smooth curves are; 5 is plenty for analysis.

Watch out

• With Dissolve result and Keep disjoint results separate, every resulting piece keeps the fid of one input feature, so several pieces share a fid and saving to a GeoPackage fails with UNIQUE constraint failed. Run Renumber feature ids (Tool - QGIS) first.
• A buffered polygon includes the original. For the zone around a shape only, see the fringe in the Proximity family.

Checked in QGIS 4.2.2, October 2026. Names and options can differ in other versions.