Intersect of all polygons from the same layer in QGIS

Question

I have various polygons within one layer in QGIS.

As a result I need the area where all polygons overlap as shown in the picture. Is there a way to do?

Answer 1

In the processing Toolbox, under SAGA, you have a treatement called polygon self-intersection which seems to be what you're seeking ...

(as a result, i seem to recall you will have a new field aggregating the id of all the polygons intersecting)

Answer 2

If you need only the geometry and not the attributes, just running normal Vector→ Geoprocessing Tools → Union with no Overlay layer [optional] should do the trick.