Background check is a step before joining the company. Generally, HR's background check is not only to understand your work ability and other situations in the previous unit through the contact information of your direct supervisor, but HR will also use the name of your previous company to activate HR's human resources network and learn about your work performance, salary income, etc. in that unit through their peers. For the ByteDance interview, if you are applying for a position of business department manager or below, it is recommended to just leave the phone number of your direct supervisor. If it is not an important management and decision-making position above the manager level, then most HR's background check is just a simple call to understand your previous work ability, and the evaluation of the former direct supervisor generally will not affect your interview and employment results. But if it is really inconvenient to leave the phone number of your direct supervisor due to "some reasons", it is recommended to leave the contact information of former colleagues or relevant leaders with whom you have a good relationship, which will be more conducive to your recruitment.