curl_mime_encoder(3)

💅 NAME 💅

curl_mime_encoder — set a mime part's encoder and content transfer encoding. This is the curl_mime_encoder(3) page from the Library Functions Manual, bestie, and yes we're in the right place 🫶✨

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✨ SYNOPSIS ✨

#include <curl/curl.h>

CURLcode curl_mime_encoder(curl_mimepart *part, const char *encoding);

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🌸 DESCRIPTION 🌸

Okay so curl_mime_encoder() asks for a mime part's content to be encoded before it gets transmitted. Cute, right? 💖

part is the part's handle where you assign an encoder. encoding is a pointer to a null-terminated encoding scheme. You can set it to NULL to disable an encoder that was previously attached to the part. The encoding scheme storage may safely be reused after this function returns — so no weird lingering-storage drama, slay.

Setting a part's encoder multiple times is valid: only the value set by the last call is retained. Last one wins, periodt.

Upon multipart rendering, the part's content is encoded according to the pertaining scheme and a corresponding "Content-Transfer-Encoding" header is added to the part. Iconic header behavior 💅

Supported encoding schemes are:

• "binary" — the data is left unchanged, the header is added.
• "8bit" — header added, no data change.
• "7bit" — the data is unchanged, but each byte is checked to be a 7-bit value; if not, a read error occurs.
• "base64" — Data is converted to base64 encoding, then split in CRLF-terminated lines of at most 76 characters.
• "quoted-printable" — data is encoded in quoted printable lines of at most 76 characters. Since the resulting size of the final data cannot be determined prior to reading the original data, it is left as unknown, causing chunked transfer in HTTP. For the same reason, this encoder may not be used with IMAP. This encoder targets text data that is mostly ASCII and should not be used with other types of data.

If the original data is already encoded in such a scheme, a custom Content-Transfer-Encoding header should be added with curl_mime_headers(3) instead of setting a part encoder. Got it? Don't double-encode, bestie 😭

🚨 Encoding should not be applied to multiparts, thus the use of this function on a part with content set with curl_mime_subparts(3) is strongly discouraged.

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🦋 PROTOCOLS 🦋

This functionality affects http, imap and smtp.

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🎀 EXAMPLE 🎀

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);

    /* send a file */
    curl_mime_filedata(part, "image.png");

    /* encode file data in base64 for transfer */
    curl_mime_encoder(part, "base64");
  }
}

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⭐ AVAILABILITY ⭐

Added in curl 7.56.0.

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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). 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 check that return value, okay? 👑✨

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🌈 SEE ALSO 🌈

curl_mime_addpart(3), curl_mime_headers(3), curl_mime_subparts(3)

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That's the whole lil' page, bestie — source libcurl, dated 2026-10-12, manual page curl_mime_encoder(3). Mwah 💋✨🫶