How to get values which changed during node edit in node api? I have a node with user entity reference field. Now I want to get newly added users id's to this node via this field in hook_node_update

What is the best way?
The $node argument to hook_node_update contains a $node-&gt;original object. With that you can identify the newly added user IDs by comparing $node-&gt;your_user_ref_field to $node-&gt;original-&gt;your_user_ref_field.