In this paper, we study the level-set of the zero-average Gaussian Free Field on a uniform random d-regular graph above an arbitrary level h ∈ (−∞, h ), where h is the level-set percolation threshold of the GFF on the d-regular tree T d . We prove that w.h.p as the number n of vertices diverges, the GFF has a unique giant connected component, where η(h) is the probability that the root percolates in the corresponding GFF level-set on T d . This gives a positive answer to the conjecture of [2] for most regular graphs. We also prove that the second largest component has size Θ(log n).
Moreover, we show that C(n) 1 shares the following similarities with the giant component of the supercritical Erdős-Rényi random graph. First, the diameter and the typical distance between vertices are Θ(log n). Second, the 2-core and the kernel encompass a given positive proportion of the vertices. Third, the local structure is a branching process conditioned to survive, namely the level-set percolation cluster of the root in T d (in the Erdős-Rényi case, it is known to be a Galton-Watson tree with a Poisson distribution for the offspring).