In HTTP headers with parameters, are parameter names case-sensitive?

Question

I know HTTP header names themselves are case-insensitive (that question has been answered multiple times), but what of parameter names within the headers? I'm talking about parts like:

• charset within the Content-Type header (the values for charset ignore case, but does the charset keyword itself?)
• filename within the Content-Disposition header

Would a server be safe in assuming these keywords will always be lowercase?

Answer 1

Since RFC 7230 HTTP/1.1 Message Syntax and Routing doesn't say anything regarding header field value, you could assume that this value is application defined. As a result, I don't think that you can be sure that this value will always be lowercase.