Sanity deduplicates identical image uploads by design - is this reliable?

Yes, you're absolutely correct! This is indeed the intended behavior, and you can safely rely on it. Sanity automatically deduplicates image assets based on their content.

When you upload an image to Sanity, the platform generates a deterministic ID based on the actual image content (using a SHA1 hash of the file). This means that uploading the exact same image multiple times will always return the same _id and url without creating duplicate asset documents in your Content Lake.

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."

The asset ID follows the format image-<sha1hash>-<dimensions>-<format>, so if the content is identical, the hash will be identical, resulting in the same asset ID. This is why your count(*[_type == "sanity.imageAsset"]) query doesn't change when you re-upload the same image.

This deduplication behavior is actually a feature that helps:

• Save storage space by avoiding duplicate files
• Maintain referential integrity (all references point to the same asset)
• Speed up migrations and bulk uploads (you can upload without worrying about creating duplicates)

So yes, you can confidently build your workflows around this behavior. It's a core part of how Sanity's asset pipeline works, designed to eliminate the burden of managing duplicate image versions. The sha1hash-based deduplication ensures that identical image content always maps to the same asset document.