We investigate the boundary trace operators that naturally correspond to$\mathrm{H}(\operatorname{curl},\Omega)$, namely the tangential and twistedtangential trace, where $\Omega \subseteq \mathbb{R}^{3}$. In particular weregard partial tangential traces, i.e., we look only on a subset $\Gamma$ ofthe boundary $\partial\Omega$. We assume both $\Omega$ and $\Gamma$ to bestrongly Lipschitz (possibly unbounded). We define the space of all$\mathrm{H}(\operatorname{curl},\Omega)$ fields that possess a $\mathrm{L}^{2}$tangential trace in a weak sense and show that the set of all smooth fields isdense in that space, which is a generalization of Belgacem, Bernardi, Costabeland Dauge 1997. This is especially important for Maxwell's equation with mixedboundary condition as we answer the open problem by Weiss and Staffans 2013(Section 5) for strongly Lipschitz pairs.