Question on CTag and Etag

Hi Venkataramanappa, Girish

I have conducted some research and to directly answer your concern:

1/ Is it expected that cTag changes for metadata-only updates such as rename or move?

Yes, in practice, this an expected behavior, specifically for SharePoint and OneDrive for Business.

While the conceptual documentation often states:

• eTag (Entity Tag): Represents the entire item (Content + Metadata).
• cTag (Content Tag): Represents just the content.

In reality, the underlying SharePoint storage engine often treats a file move or rename as an operation that creates a new version of the item or updates the internal container wrapper. Because of how tightly SharePoint couples this data, operations like renaming a file, moving it, or even sometimes updating custom columns will trigger an update to the underlying item version, which causes both the eTag and the cTag to change.

This means cTag is ultimately unreliable as a strict "content-only" change indicator in SharePoint environments.

2. How to reliably distinguish content changes from metadata changes?

Technically, since you cannot rely on cTag alone, the recommended and most robust way to detect actual binary content changes in a Delta query is to use File Hashes.

Every driveItem that is a file includes a file facet in the Graph API response, which contains a hashes object.

• For SharePoint / OneDrive for Business: You should check the quickXorHash.
• For OneDrive Personal: You would typically look at the sha1Hash or sha256Hash.

You can read here for more information: hashes resource type

3/ The recommended Delta Processing Logic:

When you process your delta responses, you should maintain a local state of both the file's metadata and its quickXorHash.

When an item appears in your Delta response, apply the following logic:

1. Compare the Hash (file.hashes.quickXorHash):
   • If the new hash differs from your stored hash, the binary content of the file has physically changed. You need to re-download or process the new file content.
   • If the new hash is exactly the same, you can guarantee that the file's binary content has not changed.
2. Check for Metadata/Move/Rename Operations:
   • If the hash is identical (no content change), but the item came back in the delta response, it was a metadata change.
   • You can then compare the newly returned name and parentReference.id against your stored state.
   • If name changed > It was a rename. If parentReference.id changed > It was moved to a different folder.

 Hope my answer will help you

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