The upload restrictions of the sina file sharing were based on the security measures and data protection policies on the server. In order to ensure the security and privacy of user data, sina file sharing will impose upload restrictions on certain types of files. For example, novel files are usually limited to a single file size that does not exceed a certain value to prevent the file from being too large and causing upload failure or malicious download by other users. There might be some technical problems with uploading a single folder. In the traditional server upload technology, every file needed to be verified and uploaded by the server. If multiple files were the same or similar, the server might combine all the upload requests into one and return a success or failure response. However, in the client-side upload technology, in order to prevent the server from merging multiple files, each file would usually be requested and verified separately to ensure that each file was independent. Therefore, in order to ensure the security and stability of the upload, sina file sharing usually limits the upload of a single folder. If you want to upload files from multiple folder, you can try to use some third-party upload tools such as FTP or SFTP to upload multiple folder in this way. However, it is important to note that this method may violate the upload restrictions of sina file sharing, so you need to bear the risk yourself.