We demonstrate the presence of modular properties in partition functions of T T deformed conformal field theories. These properties are verified explicitly for the deformed free boson. The modular features facilitate a derivation of the asymptotic density of states in these theories, which turns out to interpolate between Cardy and Hagedorn behaviours. We also point out a sub-sector of the spectrum that remains undeformed under the T T flow. Finally, we comment on the deformation of the CFT vacuum character and its implications for the holographic dual.Recently, Cardy [3] proposed a different point of view on the T T deformation. In this approach, the T T deformation is interpreted as coupling the field theory to uniform stochastic gravity. The fact that the T T deformation is solvable is because the action of the stochastic gravity is a total derivative and has little to do with integrability. At the