Line Endings
RFC 9112 Section 2.2 defines that HTTP/1.1 messages use CRLF (\r\n) as the line terminator for the request-line and header fields. Deviations from this — bare LF, bare CR — are framing violations that can lead to request smuggling or parser confusion.
The Rule
“Although the line terminator for the start-line and fields is the sequence CRLF, a recipient MAY recognize a single LF as a line terminator and ignore any preceding CR.” — RFC 9112 Section 2.2
“A sender MUST NOT generate a bare CR (a CR character not immediately followed by LF) within any protocol elements other than the content. A recipient of such a bare CR MUST consider that element to be invalid or replace each bare CR with SP before processing the element or forwarding the message.” — RFC 9112 Section 2.2