Does iterating through Azure blobs with GetBlobsAsync load large blob contents into memory?

When you use GetBlobsAsync to enumerate blobs with a specified prefix, Azure Blob Storage only returns the metadata for each blob—not the content. This means that:

• The blob content (the actual file data) is not downloaded or loaded into your application's memory.
• Only metadata (such as blob name, properties, etc.) is retrieved when iterating over the blobs.

This behavior holds regardless of the file sizes. You're just getting the blob descriptions, so you won’t run into issues with large files being loaded into memory.

How to Verify

If you want to be absolutely sure, you can monitor network traffic using tools like Fiddler or network diagnostics in your cloud environment. Additionally, you can review the Azure SDK documentation, where the description of GetBlobsAsync explicitly mentions that it retrieves blob metadata.

Here’s your code snippet with an added comment for clarity:

CSHARPCopied
int count = 0;

// Iterate through only the metadata of blobs with the specified prefix.
// This does not load blob content into memory.
await foreach (BlobItem blobItem in containerClient.GetBlobsAsync(prefix: folderPrefix))
{
    count++;
}

return count;

In summary, you can safely use the given approach knowing it only deals with the blob metadata.