Underwear over diaper.

[Canadianfalls]

Usually no, hurts my junk and unless the diaper is very loose or has bad tapes or something, it just lessens the amount of use I'll get out of it.

If it's needed, then briefs for maximum support.

 

[Binky151]

I wear tights with mine to hold it close to my body and stop it from sagging

 

[Sidewinder]

I wear boxer briefs over my diaper to keep things relatively discreet.

 

[Wetshisbed]

I don’t have any normal underwear , that got binned 2 years ago

Mine went in the rag bag years ago

 

[PupSpaz]

adding tight underwear over your diaper does seem to decrease absorbency and make it more prone to leaks, from my own experience and here's a neat YouTube video on it:

 

[SparkyDog]

I wear boxer briefs over top of my diaper
really helps keep everything in place and
cuts down on noise.