Sanity deduplicates identical image uploads by hash?

Yes, this is correct and confirmed behavior that you can rely on! Sanity implements automatic asset deduplication based on the content of the file itself.

When you upload an image to Sanity, the platform generates a deterministic ID based on the actual image content (using a SHA-1 hash). This means that uploading the exact same image multiple times will:

• Return the same _id every time (formatted as image-<sha1hash>-<dimensions>-<format>)
• Point to the same url
• Not create duplicate sanity.imageAsset documents in your Content Lake
• Keep your count(*[_type == "sanity.imageAsset"]) unchanged

As mentioned in the Sanity documentation on uploading assets efficiently, "Images uploaded to the Content Lake receive deterministic IDs based on the image content itself, ensuring that uploading the same image multiple times results in the same ID without creating duplicate documents."

This is a deliberate feature that helps prevent asset bloat and keeps your Content Lake clean. It's particularly useful when:

• Running migration scripts that might process the same images multiple times
• Multiple content editors upload the same brand assets or stock photos
• Automated systems upload images programmatically

So you can absolutely rely on this behavior in your workflows! The deduplication happens automatically at the platform level based on the file's content hash, not just the filename, so even if you upload the same image with different filenames, it will be deduplicated.