We have studied the variability of the black-widow type binary millisecond pulsar PSR J1311$-$3430 from optical to gamma-ray energies. We confirm evidence for orbital modulation in the weak off-pulse $ge$200-MeV emission, with a peak at $phi_Bapprox 0.8$, following pulsar inferior conjunction. The peak has a relatively hard spectrum, extending above $sim 1$,GeV. XMM-Newton and Swift UV observations also show that this sources strong X-ray flaring activity is associated with optical/UV flares. With a duty cycle $sim 7-19$%, this flaring is quite prominent with an apparent power-law intensity distribution. Flares are present at all orbital phases, with a slight preference for $phi_B=0.5-0.7$. We explore possible connections of these variabilities with the intrabinary shock and magnetic activity on the low mass secondary.
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