Mix mayonnaise with chopped pickles, lemon juice, dill, capers, and mustard in a small bowl until well combined.
The flavor is best if allowed to meld in the refrigerator for a few hours, but it can be enjoyed right away.
Notes
The briny capers and pickles both add salty flavor to the tartar sauce, so I don't feel adding more is needed. However, you can add a small pinch of kosher salt to your homemade sauce if you feel it would benefit from a little more salt.