.\" generated by cd2nroff 0.1 from CURLOPT_POSTFIELDSIZE.md
.TH CURLOPT_POSTFIELDSIZE 3 "2026-10-31" libcurl
.SH NAME
CURLOPT_POSTFIELDSIZE \- size of POST data pointed to
.SH SYNOPSIS
.nf
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_POSTFIELDSIZE, long size);
.fi
.SH DESCRIPTION
Set the \fIsize\fP of the data buffer to POST to prevent libcurl from doing a
strlen() to figure out the data size. When this option is used you can post
fully binary data, which otherwise is likely to fail. If this size is set to
-1, libcurl uses strlen() to get the size or relies on the
\fICURLOPT_READFUNCTION(3)\fP (if used) to signal the end of data.

You \fImust\fP make sure that the set size is not larger than the provided buffer.

If you post more than 2GB, use \fICURLOPT_POSTFIELDSIZE_LARGE(3)\fP.
.SH DEFAULT
-1
.SH PROTOCOLS
This functionality affects http, mqtt and rtsp
.SH EXAMPLE
.nf
#include <string.h> /* for strlen */

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    static const char *data = "data to send";

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

    /* size of the POST data */
    curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, (long)strlen(data));

    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data);

    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
.fi
.SH AVAILABILITY
Added in curl 7.2
.SH RETURN VALUE
\fIcurl_easy_setopt(3)\fP returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non\-zero means an error occurred, see
\fIlibcurl\-errors(3)\fP.
.SH SEE ALSO
.BR CURLOPT_POSTFIELDS (3),
.BR CURLOPT_POSTFIELDSIZE_LARGE (3)