//Getting instance FirebaseFirestore db = FirebaseFirestore.getInstance(); //Getting Reference to "users" collection, calling get to retrieve data, adding a callback db.collection("users").get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() { @Override public void onComplete(@NonNull Task<QuerySnapshot> task) { // Task complete if (task.isSuccessful()) { //Task successful //Getting each document one by one in that collection for (QueryDocumentSnapshot documentSnapshot: task.getResult()){ //Performing the delete operation documentSnapshot.getReference().delete(); } } } });