What is difference between "Custom Storage" and "Backup"?

When you are using custom storage to store files, you have to issue  copy requests via our REST API. After you issued requests, all files will be stored in your custom storage, otherwise, they will be deleted withing 24 hours after upload.

When you are using backup, all your files are stored in Uploadcare storage, and from Uploadcare storage are backed up to your custom storage. If you are using Uploadcare storage, there is no need to issue any kind of requests. Uploadcare storage and backup work simultaneously.

For more information, see storages.