How is file upload handled in HTTP?

I am curious to know how webservers handle file uploads.

Is the entire file s开发者_如何学运维ent as a single chunk? Or is it streamed into the webserver - which puts it together and saves it in a temp folder for PHP etc. to use?

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It's just a matter of following the encoding rules so that one can easily decode (parse) it. Read on the specification about multipart-form/data encoding (the one which is required in HTML based file uploads using input type="file").

Generally the parsing is done by the server side application itself. The webserver only takes care about streaming the bytes from the one to the other side.

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It's streamed to answer that question, but see this RFC 1867 for more information.

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RFC 1867 describes the mechanism.