What is a TE header?
Lists the transfer encodings the client is willing to accept in the response, beyond the default chunked.
TE is the request-side analogue of Transfer-Encoding, letting a client advertise which additional transfer codings (like trailers) it can handle beyond the default chunked encoding. It's a fairly low-level, rarely-touched header in everyday website development - most HTTP clients and servers handle it automatically without either side needing to think about it.
Common use case
An HTTP client advertises TE: trailers to tell the server it knows how to read trailing headers sent after a chunked response body, such as a checksum computed only once streaming finishes.
Example
TE: trailers, deflate;q=0.5History
Part of the original HTTP/1.1 specification, RFC 2068 (1997).
Did you know?
It is one of the few headers explicitly exempted from being forwarded end-to-end by proxies - the spec treats it as hop-by-hop, meaning each proxy must renegotiate it independently rather than just passing it along.