Trailer

Announces fields that will appear in the trailer part of a chunked message.

Use Trailer with chunked transfer coding to send metadata after the body, such as a checksum. Content-Length, Host, and other framing or control fields are forbidden in trailers.

httpheaderframingintegrity

Reference (http)

Trailer: Content-Digest
Transfer-Encoding: chunked

Use Trailer with chunked transfer coding to send metadata after the body, such as a checksum. Content-Length, Host, and other framing or control fields are forbidden in trailers.

Common mistakes

Placing framing fields such as Content-Length in a trailer, which recipients must reject.

IANA registry: http-fields/field-names

Registry reference: RFC 9110, Section 6.6.2: HTTP Semantics

Sources

MDN HTTP Reference
IANA HTTP Field Name Registry