= cowboy_req:set_resp_headers(3)

== Name

cowboy_req:set_resp_headers - Set several response headers

== Description

[source,erlang]
----
set_resp_headers(Headers, Req :: cowboy_req:req())
    -> Req

Headers :: cowboy:http_headers() | [{binary(), iodata()}]
----

Set several headers to be sent with the response.

The header name must be given as a lowercase binary string.
While header names are case insensitive, Cowboy requires them
to be given as lowercase to function properly.

Cowboy does not allow duplicate header names. Headers set
by this function may be overwritten by those set from the
reply functions. Likewise, headers set by this function may
overwrite headers that were set previously.

Use link:man:cowboy_req:set_resp_cookie(3)[cowboy_req:set_resp_cookie(3)]
instead of this function to set cookies.

== Arguments

Headers::

Headers as a map with names being lowercase binary strings,
and values as iodata; or as a list with the same requirements
for names and values.
+
When a list is given it is converted to its equivalent map,
with duplicate headers concatenated with a comma inserted
in-between. Support for lists is meant to simplify using
data from clients or other applications.
+
The set-cookie header must not be set using this function.

Req::

The Req object.

== Return value

A new Req object is returned.

The returned Req object must be used from that point onward,
otherwise the headers will not be sent in the response.

== Changelog

* *2.13*: The function now accepts a list of headers.
* *2.0*: Function introduced.

== Examples

.Set several response headers
[source,erlang]
----
Req = cowboy_req:set_resp_headers(#{
    <<"content-type">>     => <<"text/html">>,
    <<"content-encoding">> => <<"gzip">>
}, Req0).
----

== See also

link:man:cowboy_req(3)[cowboy_req(3)],
link:man:cowboy_req:set_resp_cookie(3)[cowboy_req:set_resp_cookie(3)],
link:man:cowboy_req:set_resp_header(3)[cowboy_req:set_resp_header(3)],
link:man:cowboy_req:has_resp_header(3)[cowboy_req:has_resp_header(3)],
link:man:cowboy_req:resp_header(3)[cowboy_req:resp_header(3)],
link:man:cowboy_req:resp_headers(3)[cowboy_req:resp_headers(3)],
link:man:cowboy_req:delete_resp_header(3)[cowboy_req:delete_resp_header(3)],
link:man:cowboy_req:reply(3)[cowboy_req:reply(3)],
link:man:cowboy_req:stream_reply(3)[cowboy_req:stream_reply(3)]