  The congruence subgroups of braid groups arise from a congruence condition on
the integral Burau representation $B_n \to \operatorname{GL}_{n}(\mathbb Z)$.
We find the image of such congruence subgroups in
$\operatorname{GL}_{n}(\mathbb Z)$-an open problem posed by Dan Margalit.
Additionally, we characterize the quotients of braid groups by their congruence
subgroups in terms of symplectic congruence subgroups.
