A Shared Access Signature (SAS) URL is a URI that grants restricted access rights to Azure storage resources. It allows you to delegate access to containers and blobs within your storage account without sharing your account keys.

With a SAS URL, you can:

• Manage permissions: Specify read, write, delete, or list access. In Flow, the default permissions are read/write.
• Set expiration: Limit the duration of access by setting an expiration time. In Flow, by default, the URL will never expire.

Use Cases for SAS URLs

• External App Uploads: Use SAS URLs to securely allow external Azure apps or users to upload files directly to Blob Storage.
• Managed Uploads: Enable secure file uploads from web or mobile applications without embedding sensitive credentials.

Default Configuration for SAS URL:

Permissions: Ensure that the SAS token has the appropriate permissions, such as read, write, and list.

Expiry Time: Set an appropriate expiration time for the SAS token to limit how long the URL can be used. 

Resource Type: Specify the type of resource (container or blob) the SAS URL will access. 

Protocols: Define the protocols (HTTP or HTTPS) that are allowed to access the storage resources.