Images will be stored in the cloud service of which you are using to connect with AppSheet. E.g if you are logging in with a Gmail account, the images will be stored on Google Drive. If you are using a Microsoft login, they are stored on Onedrive, etc.
While storing images directly in the db can be done, it is super inefficient. It is best to store the URL in the db and then locate the image in a File system. File systems are typically optimized to handle these files better than a db and its much simpler to expand the storage when needed.
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