CURLOPT_ERRORBUFFER(3)

CURLOPT_ERRORBUFFER(3) 💅

okay so like, welcome to the CURLOPT_ERRORBUFFER(3) page, straight out of the Library Functions Manual ✨. This is the option that gives libcurl somewhere cute and safe to spill the tea when something goes wrong.

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💖 NAME 💖

CURLOPT_ERRORBUFFER — error buffer for error messages. periodt.

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✨ SYNOPSIS ✨

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_ERRORBUFFER, char *buf);

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🌸 DESCRIPTION 🌸

Bestie, you pass a char pointer to a buffer that libcurl may use to store human readable error messages on failures or problems. This may be more helpful than just the return code from curl_easy_perform(3) and related functions. The buffer must be at least CURL_ERROR_SIZE bytes big — no skimping, okay? 💅

Now the part where you gotta be responsible: you must keep the associated buffer available until libcurl no longer needs it. Failing to do so might cause odd behavior or even crashes 😭. libcurl might need it until you call curl_easy_cleanup(3) or you set the same option again to use a different pointer.

Also, do not rely on the contents of the buffer unless an error code was returned. Since 7.60.0 libcurl initializes the contents of the error buffer to an empty string before performing the transfer. For earlier versions if an error code was returned but there was no error detail then the buffer was untouched.

Do not attempt to set the contents of the buffer yourself, including in any callbacks you write that may be called by libcurl. The library may overwrite the buffer after your callback returns — so hands off, okay? 🙈

Consider CURLOPT_VERBOSE(3) and CURLOPT_DEBUGFUNCTION(3) to better debug and trace why errors happen. They are literally the detective duo for your curl drama 🔍✨.

Using this option multiple times makes the last set pointer override the previous ones. Set it to NULL to disable its use again.

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🎀 DEFAULT 🎀

NULL

That’s it. NULL. iconic minimalism 💀.

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🦋 PROTOCOLS 🦋

This functionality affects all supported protocols. all of them. universal slay 🌈.

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🔥 EXAMPLE 🔥

Here’s the example, verbatim, because you deserve the whole thing 🍓:

#include <string.h> /* for strlen() */
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    char errbuf[CURL_ERROR_SIZE];

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

    /* provide a buffer to store errors in */
    curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, errbuf);

    /* set the error buffer as empty before performing a request */
    errbuf[0] = 0;

    /* perform the request */
    result = curl_easy_perform(curl);

    /* if the request did not complete correctly, show the error
    information. if no detailed error information was written to errbuf
    show the more generic information from curl_easy_strerror instead.
    */
    if(result != CURLE_OK) {
      size_t len = strlen(errbuf);
      fprintf(stderr, "\nlibcurl: (%d) ", result);
      if(len)
        fprintf(stderr, "%s%s", errbuf,
                ((errbuf[len - 1] != '\n') ? "\n" : ""));
      else
        fprintf(stderr, "%s\n", curl_easy_strerror(result));
    }
  }
}

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💜 AVAILABILITY 💜

Added in curl 7.1 🎀.

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⭐ RETURN VALUE ⭐

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).

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🌈 SEE ALSO 🌈

• CURLOPT_DEBUGFUNCTION(3)
• CURLOPT_VERBOSE(3)
• curl_easy_strerror(3)
• curl_multi_strerror(3)
• curl_share_strerror(3)
• curl_url_strerror(3)

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xoxo, the libcurl manual, dated 2026-10-12 🫶💋