In this talk I will describe co-dimension 2 and 4 defects in 6d (2,0) theories in several points of view: 3d SL(N,C) Chern-Simons theory (state-integral model, cluster algebra), 3d N=2 field theory, 5d N=2 super Yang-Mills, and AdS4 holographic dual. This leads to quantitative consistency checks of different approaches, as well as new predictions for a variety of partition functions.