curl_mime_type(3)

💅 curl_mime_type(3) — like, the mime type setter bestie

okay so this is curl_mime_type(3), from the libcurl Library Functions Manual, and it's genuinely one of the most useful little functions ever — it sets a mime part's content type. that's it. that's the whole vibe. 🎀

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✨ NAME ✨

curl_mime_type — set a mime part's content type. iconic behavior, no notes.

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✨ SYNOPSIS ✨

#include <curl/curl.h>

CURLcode curl_mime_type(curl_mimepart *part, const char *mimetype);

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✨ DESCRIPTION ✨

curl_mime_type(3) sets a mime part's content type. slay.

part is the part's handle you're assigning the content type to. that's your main character right there.

mimetype points to the null-terminated file mime type string — and yes, it may be set to NULL if you want to remove a previously attached mime type. poof, gone, no cap. 🙈

the mime type string is copied into the part, so the associated storage may safely be released or reused after the call. literally free yourself from worrying about it 💖. setting a part's type multiple times is valid: only the value set by the last call is retained. last one wins, periodt.

when there's no mime type set and the protocol specifications need one, a default mime type gets determined by the context:

• if set as a custom header, use this value.
• application/form-data for an HTTP form post.
• if a remote filename is set, the mime type is taken from the filename extension, or application/octet-stream by default.
• for a multipart part, multipart/mixed.
• text/plain in other cases.

ok so those defaults are not our problem, they just happen. but knowing them is highkey useful, iykyk 🦋

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✨ PROTOCOLS ✨

this functionality affects http, imap and smtp 🌈

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✨ EXAMPLE ✨

like, here's the whole thing in action:

int main(void)
{
  curl_mime *mime;
  curl_mimepart *part;

  CURL *curl = curl_easy_init();
  if(curl) {
    /* create a mime handle */
    mime = curl_mime_init(curl);

    /* add a part */
    part = curl_mime_addpart(mime);

    /* get data from this file */
    curl_mime_filedata(part, "image.png");

    /* content-type for this part */
    curl_mime_type(part, "image/png");

    /* set name */
    curl_mime_name(part, "image");
}
}

(it really does just end like that, the braces said what they said 💀)

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✨ AVAILABILITY ✨

added in curl 7.56.0 — a certified classic at this point 👑

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✨ 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). and if CURLOPT_ERRORBUFFER(3) was set with curl_easy_setopt(3) there can be an error message stored in the error buffer when non-zero is returned. so you get receipts, bestie 🧚

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✨ SEE ALSO ✨

curl_mime_addpart(3), curl_mime_data(3), curl_mime_name(3)

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that's the whole page, and honestly? obsessed. this came to you from libcurl, dated 2026-10-12 — go forth and set those mime types, bestie, you're literally gonna slay 💜🫶✨