ARTICLE AD BOX
According to a comment in response to List is null for large files. Reproducible at will : -
Yes... the actual spec: datatracker.ietf.org/doc/html/rfc7578 - when a request is using multipart/form-data it's a serialization-by-concatenation, i.e. everything arrives in-sequence. There's no interleaving, chunking, or overlapping of the data here - nor are there any concurrent requests. Now, ASP.NET Core's FormFile binder will buffer-to-memory/disk each file as it comes in, but IIRC there's no guarantee that your Controller Action will be entered-into after all uploaded files have been buffered-away. – Dai CommentedDec 12, 2025 at 7:23
But since HTTP2, opinions coalesce around "modern browsers like Chrome, Firefox, and Edge can upload multiple files using INPUT TYPE="FILE" with the multiple attribute in parallel with HTTP/2. This is achieved through multiplexing, a key feature of HTTP/2 that allows multiple requests and responses to be sent simultaneously over a single TCP connection."
Which is correct?
I know that, if multiplexing is going on there is still a sync point at the server where all files must be uploaded before they are presented in the "Files" argument but how can I prove that the browser is pumping multiple files (if available) across the network at the same time?
I've tried uploading two 1GB files and seeing if there are any temp files on the client, but couldn't find any.
Any documentation available except a stale RFC?
