We prove that SLE for $\kappa \in (4,8)$ on an independent $\gamma =4/\kappa$-Liouville quantum gravity (LQG) surface is uniquely characterized by the form of its LQG boundary length process and the form of the conditional law of the unexplored quantum surface given the explored curve-decorated quantum surface up to each time $t$. We prove variants of this characterization for both whole-plane space-filling SLE on an infinite-volume LQG surface and for chordal SLE on a finite-volume LQG surface with boundary. Using the equivalence of Brownian and $8/3$-LQG surfaces, we deduce that SLE$6$ on the Brownian disk is uniquely characterized by the form of its boundary length process and that the complementary connected components of the curve up to each time $t$ are themselves conditionally independent Brownian disks given this boundary length process.

The results of this paper are used in another paper by the same authors to show that the scaling limit of percolation on random quadrangulations is given by SLE$6$ on $8/3$-LQG with respect to the Gromov-Hausdorff-Prokhorov-uniform topology, the natural analog of the Gromov-Hausdorff topology for curve-decorated metric measure spaces.