curl\_mime\_headers(3) Library Functions Manual curl\_mime\_headers(3)

# [NAME](#NAME)

curl\_mime\_headers - set a mime part's custom headers

# [SYNOPSIS](#SYNOPSIS)

```
#include <curl/curl.h>
CURLcode curl_mime_headers(curl_mimepart *part,


                           struct curl_slist *headers, int take_ownership);
```

# [DESCRIPTION](#DESCRIPTION)

[*curl\_mime\_headers(3)*](/man/os/curl/curl_mime_headers.3) sets a mime part's custom headers.

*part* is the part's handle to assign the custom headers list to.

*headers* is the head of a list of custom headers; it may be set to NULL to remove a previously attached custom header list.

*take\_ownership*: when non-zero, causes the list to be freed upon replacement or mime structure deletion; in this case the list must not be freed explicitly.

Setting a part's custom headers list multiple times is valid: only the value set by the last call is retained.

# [PROTOCOLS](#PROTOCOLS)

This functionality affects http, imap and smtp

# [EXAMPLE](#EXAMPLE)

```
int main(void)
{


  struct curl_slist *headers = NULL;


  CURL *easy = curl_easy_init();


  curl_mime *mime;


  curl_mimepart *part;


  headers = curl_slist_append(headers, "Custom-Header: mooo");


  mime = curl_mime_init(easy);


  part = curl_mime_addpart(mime);


  /* use these headers in the part, takes ownership */


  curl_mime_headers(part, headers, 1);


  /* pass on this data */


  curl_mime_data(part, "12345679", CURL_ZERO_TERMINATED);


  /* set name */


  curl_mime_name(part, "numbers");


  /* Post and send it. */


  curl_easy_setopt(easy, CURLOPT_MIMEPOST, mime);


  curl_easy_setopt(easy, CURLOPT_URL, "https://example.com");


  curl_easy_perform(easy);
}
```

# [AVAILABILITY](#AVAILABILITY)

Added in curl 7.56.0

# [RETURN VALUE](#RETURN_VALUE)

This function returns a CURLcode indicating success or error.

CURLE\_OK (0) means everything was OK, non-zero means an error occurred, see [*libcurl-errors(3)*](/man/os/curl/libcurl-errors.3). If [*CURLOPT\_ERRORBUFFER(3)*](/man/os/curl/CURLOPT_ERRORBUFFER.3) was set with [*curl\_easy\_setopt(3)*](/man/os/curl/curl_easy_setopt.3) there can be an error message stored in the error buffer when non-zero is returned.

# [SEE ALSO](#SEE_ALSO)

[**curl\_mime\_addpart**(3)](/man/os/curl/curl_mime_addpart.3), [**curl\_mime\_name**(3)](/man/os/curl/curl_mime_name.3)

2026-10-22 libcurl

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Document: curl_mime_headers(3) from curl 8.23.0-r2 (Chainguard OS)
Source: https://github.com/curl/curl.git