[Qgis-user] Self Intersections: Issues with Polygon Features

[Andrea Giudiceandrea]

> Isenmann, Werner (RPF) Werner.Isenmann at rpf.bwl.de
> Thu Jul 3 07:11:07 PDT 2025

 > Does anyone know a good solution for repairing (many) 
self-intersections with high performance in QGIS?

Hi Werner,
which QGIS version exactly are you using and on which operative system? 
Which GDAL and GEOS libraries is QGIS using?

QGIS has a processing algorithm specifically intended to fix invalid 
geometry:
"Vector geometry - Fix geometries"
https://docs.qgis.org/3.40/en/docs/user_manual/processing_algs/qgis/vectorgeometry.html#fix-geometries

As suggested by Nigel, you could also use the trick of using the "Vector 
geometry - Buffer" processing algorithm with the "Distance" parameter 
set to the value 0.

If you are using QGIS 3.44, then you can also use the "Fix Geometry - 
Split self-intersecting geometries" processing algorithm.

If you are experiencing some issue running the "Vector geometry - Check 
validity" processing algorithm (which however is not intended to fix 
invalid geometries) it would be useful if you reported such issue at 
https://github.com/qgis/QGIS/issues

In order to search for self-intersecting geometries, you could also use 
the "Check Geometry - Self-intersections" processing algorithm (QGIS >= 
3.44).

Best regards.

Andrea Giudiceandrea