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

# [NAME](#NAME)

CURLOPT\_POSTFIELDSIZE\_LARGE - size of POST data pointed to

# [SYNOPSIS](#SYNOPSIS)

```
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_POSTFIELDSIZE_LARGE,


                          curl_off_t size);
```

# [DESCRIPTION](#DESCRIPTION)

Set the *size* 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 [*CURLOPT\_READFUNCTION(3)*](/man/os/curl/CURLOPT_READFUNCTION.3) (if used) to signal the end of data.

You *must* make sure that the set size is not larger than the provided buffer.

# [DEFAULT](#DEFAULT)

-1

# [PROTOCOLS](#PROTOCOLS)

This functionality affects http, mqtt and rtsp

# [EXAMPLE](#EXAMPLE)

```
extern char *large_chunk; /* pointer to somewhere */
int main(void)
{


  CURL *curl = curl_easy_init();


  if(curl) {


    CURLcode result;


    const char *data = large_chunk;


    curl_off_t length_of_data = 12345; /* set somehow */


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


    /* size of the POST data */


    curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE_LARGE, length_of_data);


    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data);


    result = curl_easy_perform(curl);


    curl_easy_cleanup(curl);


  }
}
```

# [AVAILABILITY](#AVAILABILITY)

Added in curl 7.11.1

# [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\_COPYPOSTFIELDS**(3)](/man/os/curl/CURLOPT_COPYPOSTFIELDS.3), [**CURLOPT\_POSTFIELDS**(3)](/man/os/curl/CURLOPT_POSTFIELDS.3), [**CURLOPT\_POSTFIELDSIZE**(3)](/man/os/curl/CURLOPT_POSTFIELDSIZE.3)

2026-10-22 libcurl

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Document: CURLOPT_POSTFIELDSIZE_LARGE(3) from curl 8.23.0-r2 (Chainguard OS)
Source: https://github.com/curl/curl.git