Where does inserting a value happen faster: in a linked list or in an array?

In a linked list.

Inserting an element in the middle of an array requires shifting all subsequent elements to make space. In a linked list, it is enough to change the links of the neighboring nodes, which takes constant time (O(1)). Inserting at the beginning or end of a linked list is also constant, while inserting at the beginning of an array requires shifting all elements (O(n)).

In the case of an array, even if the capacity is insufficient, a new array with greater capacity must be created and all elements copied from the old one, which is a time-consuming operation (O(n)).