  In this review, after a general introduction to the effective string theory
(EST) description of confinement in pure gauge theories, we discuss the
behaviour of EST as the temperature is increased. We show that, as the
deconfinement point is approached from below, several universal features of
confining gauge theories, like the ratio $T_c/\sqrt{\sigma_0}$, the linear
increase of the squared width of the flux tube with the interquark distance, or
the Temperature dependence of the interquark potential, can be accurately
predicted by the effective string. Moreover in the vicinity of the
deconfinement point the EST behaviour turns out to be in good agreement with
what predicted by conformal invariance or by dimensional reduction, thus
further supporting the validity of and EST approach to confinement.
