Q. How many entries can be registered to the Address book at maximum? You can register up to 5,000 entries. Related articles Q. What is Address book? How do you use it? Q. What is an Address book tag? Q. What is the uploading/downloading of the Address book file? Q. What is the CSV format used to upload/download the Address book file? Q. How do I change the information registered to my Yu ID (your profile)?