What's the difference between the SharedAccessBlobPermissions values Add, Create and Write?

Question

The possible values for SharedAccessBlobPermissions are:

• None (0)
• Read (1)
• Write (2)
• Delete (4)
• List (8)
• Add (16)
• Create (32)

What are the differences between Add, Create and Write? I can't find any documentation that clarifies this.

Answer 1

You can find information about these permissions here: https://msdn.microsoft.com/en-us/library/azure/dn140255.aspx.

From what I understand reading about these permissions:

• Add: Add permission is only applicable for append blobs. You use this permission to add a block to an append blob. No other operation is possible using this permission.
• Create: Create permission only allows creation of blobs or in other words you can't update a blob with this permission. This would include writing a new blob, take a snapshot of an existing blob, or copy a blob to a new blob.
• Write: Write permission allows creation and updation of blobs. This would include create or write content, properties, metadata, or block list, take a snapshot or manage lease on a blob and resize the blob (page blob only).

In our application, we use Shared Access Signature extensively and we make use of Write permission almost exclusively on all the blob related operations.