---
name: "CURLOPT_HEADEROPT"
section: "3"
platform: "macos"
package: "curl"
version: "166.0.0.0.1"
release: "macOS 26.5"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_HEADEROPT"
---

# CURLOPT\_HEADEROPT(3)

send HTTP headers to both proxy and host or separately

## NAME

CURLOPT\_HEADEROPT - send HTTP headers to both proxy and host or separately

## SYNOPSIS

```
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HEADEROPT, long bitmask);
```

## DESCRIPTION

Pass a long that is a bitmask of options of how to deal with headers. The two mutually exclusive options are:

**CURLHEADER\_UNIFIED** - the headers specified in *[CURLOPT\_HTTPHEADER(3)](/CURLOPT_HTTPHEADER/3.md)* are used in requests both to servers and proxies. With this option enabled, *[CURLOPT\_PROXYHEADER(3)](/CURLOPT_PROXYHEADER/3.md)* does not have any effect.

**CURLHEADER\_SEPARATE** - makes *[CURLOPT\_HTTPHEADER(3)](/CURLOPT_HTTPHEADER/3.md)* headers only get sent to a server and not to a proxy. Proxy headers must be set with *[CURLOPT\_PROXYHEADER(3)](/CURLOPT_PROXYHEADER/3.md)* to get used. Note that if a non-CONNECT request is sent to a proxy, libcurl sends both server headers and proxy headers. When doing CONNECT, libcurl sends *[CURLOPT\_PROXYHEADER(3)](/CURLOPT_PROXYHEADER/3.md)* headers only to the proxy and then *[CURLOPT\_HTTPHEADER(3)](/CURLOPT_HTTPHEADER/3.md)* headers only to the server.

## DEFAULT

CURLHEADER\_SEPARATE (changed in 7.42.1, used CURLHEADER\_UNIFIED before then)

## PROTOCOLS

HTTP

## EXAMPLE

```
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode ret;
    struct curl_slist *list;
    list = curl_slist_append(NULL, "Shoesize: 10");
    list = curl_slist_append(list, "Accept:");
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
    curl_easy_setopt(curl, CURLOPT_PROXY, "http://localhost:8080");
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, list);
    /* HTTPS over a proxy makes a separate CONNECT to the proxy, so tell
       libcurl to not send the custom headers to the proxy. Keep them
       separate! */
    curl_easy_setopt(curl, CURLOPT_HEADEROPT, CURLHEADER_SEPARATE);
    ret = curl_easy_perform(curl);
    curl_slist_free_all(list);
    curl_easy_cleanup(curl);
  }
}
```

## AVAILABILITY

Added in 7.37.0

## RETURN VALUE

Returns CURLE\_OK if the option is supported, and CURLE\_UNKNOWN\_OPTION if not.

## SEE ALSO

[**CURLOPT\_HTTPHEADER**(3)](/CURLOPT_HTTPHEADER/3.md), [**CURLOPT\_PROXYHEADER**(3)](/CURLOPT_PROXYHEADER/3.md)