  In this paper, we study the following fractional Choquard-type equation with
prescribed mass
  \begin{align*}
  \begin{cases}
  (-\Delta)^{1/2}u=\lambda u +(I_\mu*F(u))f(u),\ \ \mbox{in}\ \mathbb{R},
  \displaystyle\int_{\mathbb{R}}|u|^2 \mathrm{d}x=a^2,
  \end{cases}
  \end{align*} where $(-\Delta)^{1/2}$ denotes the $1/2$-Laplacian operator,
$a>0$, $\lambda\in \mathbb{R}$, $I_\mu(x)=\frac{{1}}{{|x|^\mu}}$ with
$\mu\in(0,1)$, $F(u)$ is the primitive function of $f(u)$, and $f$ is a
continuous function with exponential critical growth in the sense of the
Trudinger-Moser inequality. By using a minimax principle based on the homotopy
stable family, we obtain that there is at least one normalized ground state
solution to the above equation.
