Chunking - if any - is transparent and you'd have to check the options on your server and/or client to be sure.
Functionally speaking, a web request is a single unit - headers, cookies, form fields, uploads, everything is a single datastream unit. The multipart form uses special delimiters to inform the recipient where the the beginning and ending of the upload content is within the request datastream, but it's all transmitted as a single unit. That's one reason why upload progress bars have trouble working. The entire request has to be received before the webapp can respond to it.
Loudly announcing something is true and finding out you're wrong makes you feel foolish.
Finding out you're wrong and refusing to admit it makes you LOOK foolish.
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