CURLOPT\_POSTFIELDSIZE(3) Library Functions Manual CURLOPT\_POSTFIELDSIZE(3)

# [NAME](#NAME)

CURLOPT\_POSTFIELDSIZE - size of POST data pointed to

# [SYNOPSIS](#SYNOPSIS)

```
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_POSTFIELDSIZE, long size);
```

# [DESCRIPTION](#DESCRIPTION)

If you want to post static data to the server without having libcurl do a strlen() to measure the data size, this option must be used. 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 [*CURLOPT\_READFUNCTION(3)*](/man/os/curl/CURLOPT_READFUNCTION.3) (if used) to signal the end of data.

If you post more than 2GB, use [*CURLOPT\_POSTFIELDSIZE\_LARGE(3)*](/man/os/curl/CURLOPT_POSTFIELDSIZE_LARGE.3).

# [DEFAULT](#DEFAULT)

-1

# [PROTOCOLS](#PROTOCOLS)

This functionality affects http, mqtt and rtsp

# [EXAMPLE](#EXAMPLE)

```
#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);


  }
}
```

# [AVAILABILITY](#AVAILABILITY)

Added in curl 7.2

# [RETURN VALUE](#RETURN_VALUE)

[*curl\_easy\_setopt(3)*](/man/os/curl/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)*](/man/os/curl/libcurl-errors.3).

# [SEE ALSO](#SEE_ALSO)

[**CURLOPT\_POSTFIELDS**(3)](/man/os/curl/CURLOPT_POSTFIELDS.3), [**CURLOPT\_POSTFIELDSIZE\_LARGE**(3)](/man/os/curl/CURLOPT_POSTFIELDSIZE_LARGE.3)

2026-09-24 libcurl

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Document: CURLOPT_POSTFIELDSIZE(3) from curl 8.22.0-r3 (Chainguard OS)
Source: https://github.com/curl/curl.git