1CURLOPT_HTTPHEADER(3) curl_easy_setopt options CURLOPT_HTTPHEADER(3)
2
6 CURLOPT_HTTPHEADER - set of HTTP headers
7
9 #include <curl/curl.h>
10 CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTPHEADER,
12 struct curl_slist *headers);
13
15 Pass a pointer to a linked list of HTTP headers to pass to the server
16 and/or proxy in your HTTP request. The same list can be used for both
17 host and proxy requests!
18 When used within an IMAP or SMTP request to upload a MIME mail, the
20 given header list establishes the document-level MIME headers to
21 prepend to the uploaded document described by CURLOPT_MIMEPOST(3). This
22 does not affect raw mail uploads.
23 The linked list should be a fully valid list of struct curl_slist
25 structs properly filled in. Use curl_slist_append(3) to create the list
26 and curl_slist_free_all(3) to clean up an entire list. If you add a
27 header that is otherwise generated and used by libcurl internally, your
28 added one will be used instead. If you add a header with no content as
29 in 'Accept:' (no data on the right side of the colon), the internally
30 used header will get disabled. With this option you can add new head‐
31 ers, replace internal headers and remove internal headers. To add a
32 header with no content (nothing to the right side of the colon), use
33 the form 'name;' (note the ending semicolon).
34 The headers included in the linked list must not be CRLF-terminated,
36 because libcurl adds CRLF after each header item. Failure to comply
37 with this will result in strange bugs because the server will most
38 likely ignore part of the headers you specified.
39 The first line in an HTTP request (containing the method, usually a GET
41 or POST) is not a header and cannot be replaced using this option. Only
42 the lines following the request-line are headers. Adding this method
43 line in this list of headers will only cause your request to send an
44 invalid header. Use CURLOPT_CUSTOMREQUEST(3) to change the method.
45 When this option is passed to curl_easy_setopt(3), libcurl will not
47 copy the entire list so you must keep it around until you no longer use
48 this handle for a transfer before you call curl_slist_free_all(3) on
49 the list.
50 Pass a NULL to this option to reset back to no custom headers.
52 The most commonly replaced HTTP headers have "shortcuts" in the options
54 CURLOPT_COOKIE(3), CURLOPT_USERAGENT(3) and CURLOPT_REFERER(3). We rec‐
55 ommend using those.
56 There's an alternative option that sets or replaces headers only for
58 requests that are sent with CONNECT to a proxy: CURLOPT_PROXYHEADER(3).
59 Use CURLOPT_HEADEROPT(3) to control the behavior.
60
62 Setting some specific headers will cause libcurl to act differently.
63 Host: The specified host name will be used for cookie matching if the
65 cookie engine is also enabled for this transfer. If the request
66 is done over HTTP/2 or HTTP/3, the custom host name will instead
67 be used in the ":authority" header field and Host: will not be
68 sent at all over the wire.
69 Transfer-Encoding: chunked
71 Tells libcurl the upload is to be done using this chunked encod‐
72 ing instead of providing the Content-Length: field in the re‐
73 quest.
74
76 When used to build a MIME e-mail for IMAP or SMTP, the following docu‐
77 ment-level headers can be set to override libcurl-generated values:
78 Mime-Version:
80 Tells the parser at the receiving site how to interpret the MIME
81 framing. It defaults to "1.0" and should normally not be al‐
82 tered.
83 Content-Type:
85 Indicates the document's global structure type. By default,
86 libcurl sets it to "multipart/mixed", describing a document made
87 of independent parts. When a MIME mail is only composed of al‐
88 ternative representations of the same data (i.e.: HTML and plain
89 text), this header must be set to "multipart/alternative". In
90 all cases the value must be of the form "multipart/*" to respect
91 the document structure and may not include the "boundary=" pa‐
92 rameter.
93 Other specific headers that do not have a libcurl default value but are
95 strongly desired by mail delivery and user agents should also be in‐
96 cluded. These are "From:", "To:", "Date:" and "Subject:" among others
97 and their presence and value is generally checked by anti-spam utili‐
98 ties.
99
101 By default, this option makes libcurl send the given headers in all
102 HTTP requests done by this handle. You should therefore use this option
103 with caution if you for example connect to the remote site using a
104 proxy and a CONNECT request, you should to consider if that proxy is
105 supposed to also get the headers. They may be private or otherwise sen‐
106 sitive to leak.
107 Use CURLOPT_HEADEROPT(3) to make the headers only get sent to where you
109 intend them to get sent.
110 Custom headers are sent in all requests done by the easy handles, which
112 implies that if you tell libcurl to follow redirects (CURLOPT_FOLLOWLO‐
113 CATION(3)), the same set of custom headers will be sent in the subse‐
114 quent request. Redirects can of course go to other hosts and thus those
115 servers will get all the contents of your custom headers too.
116 Starting in 7.58.0, libcurl will specifically prevent "Authorization:"
118 headers from being sent to other hosts than the first used one, unless
119 specifically permitted with the CURLOPT_UNRESTRICTED_AUTH(3) option.
120 Starting in 7.64.0, libcurl will specifically prevent "Cookie:" headers
122 from being sent to other hosts than the first used one, unless specifi‐
123 cally permitted with the CURLOPT_UNRESTRICTED_AUTH(3) option.
124
126 NULL
127
129 HTTP, IMAP and SMTP
130
132 CURL *curl = curl_easy_init();
133 struct curl_slist *list = NULL;
135 if(curl) {
137 curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
138 list = curl_slist_append(list, "Shoesize: 10");
140 list = curl_slist_append(list, "Accept:");
141 curl_easy_setopt(curl, CURLOPT_HTTPHEADER, list);
143 curl_easy_perform(curl);
145 curl_slist_free_all(list); /* free the list */
147 }
148
151 As long as HTTP is enabled. Use in MIME mail added in 7.56.0.
152
154 Returns CURLE_OK if HTTP is supported, and CURLE_UNKNOWN_OPTION if not.
155
157 CURLOPT_CUSTOMREQUEST(3), CURLOPT_HEADEROPT(3), CURLOPT_PROXYHEADER(3),
158 CURLOPT_HEADER(3), CURLOPT_MIMEPOST(3), curl_mime_init(3)
159libcurl 8.0.1 January 02, 2023 CURLOPT_HTTPHEADER(3)