What is Context Filter?

A context filter is one you promote above the ordinary dimension filters so that everything else operates on its result.

Tableau builds a temporary table containing only the rows that pass the context filter, and every subsequent filter, top-N rule and FIXED calculation works against that subset.

The classic reason to use one is top-N. If you filter to the top 10 products and separately filter to one region, the top 10 is computed across *all* regions and then intersected with the region — usually not what was intended. Putting the region filter in context computes the top 10 within that region.

Add one by right-clicking the field on the Filters shelf and choosing Add to Context. The pill turns grey.