# What is the vertical asymptote of a log function?

Logarithm functions are defined on $\left(0 , \infty\right)$ and they have an infinite limit at ${0}^{+}$ (namely, $- \infty$ if the base is greater than 1, and $\infty$ if the base is between 0 and 1).
Thus, the $y$-axis, $x = 0$ is the vertical asymptote.