---
name: "curl_mime_headers"
section: "3"
platform: "linux"
package: "curl"
version: "8.23.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/curl_mime_headers"
---

# curl\_mime\_headers(3)

set a mime part's custom headers

## NAME

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

## SYNOPSIS

```
#include <curl/curl.h>
CURLcode curl_mime_headers(curl_mimepart *part,
                           struct curl_slist *headers, int take_ownership);
```

## DESCRIPTION

*[curl\_mime\_headers(3)](/curl_mime_headers/3.md)* 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

This functionality affects http, imap and smtp

## 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

Added in curl 7.56.0

## 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)](/libcurl-errors/3.md)*. If *[CURLOPT\_ERRORBUFFER(3)](/CURLOPT_ERRORBUFFER/3.md)* was set with *[curl\_easy\_setopt(3)](/curl_easy_setopt/3.md)* there can be an error message stored in the error buffer when non-zero is returned.

## SEE ALSO

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