Capilization of Header fields


I’m finding that Cloudflare is changing some headers which is causing us some pain with one of our Applications.

The header is “File-Size” and need it to be “file-size”. When I check within my network it does return all lower case for the header filed.
However when I test it going through an Cloudflare Tunnel , it returns the “File-Size”.
I’m using postman for testing.

Any ideas?


This may be due to the differences between HTTP/1.1 and HTTP/2.

All header names in HTTP/2 are lower case, and CF will convert if needed.

All headers comparisons in HTTP/1.1 should be case insensitive anyway, so the change in H/2 should not matter terribly much.


Thanks Michael.
Not sure what you mean by “and CF will convert if needed”. I would prefer CF to leave my headers along especially custom headers.
I assume I can override this behavior with page rules and HTTP header modifications?


If a user makes a request over HTTP/2 then all response headers will be sent lowercase, regardless of what your origin said over a HTTP/1.1 Origin response. This is part of the HTTP/2 specification, and that behaviour cannot be modified, unless you disable H2 (which is not possible on a free plan).


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