Check how an Arweave upload will be served over HTTP

An Arweave transaction can carry a Content-Type tag that affects the HTTP response for its data. A correct byte upload may still be presented with an unintended media type.

Validate the tag before signing

For a PNG asset, check the encoded file's signature and set the tag value to image/png before signing. Read the data through the ordinary content URL and inspect both the HTTP header and file prefix. Without the content-type tag, the documented default is application/octet-stream.

signed tag: Content-Type = image/png
payload prefix (hex): 89 50 4e 47 0d 0a 1a 0a
readback: compare HTTP header and decoded bytes

Distinguish metadata from file contents

A correct header cannot turn malformed bytes into a PNG or establish that decoding the asset is safe. A gateway override may also affect the response header. Inspect the signed transaction tags when diagnosing a discrepancy between two gateways serving the same transaction.

Sources