---
name: "CURLOPT_TFTP_BLKSIZE"
section: "3"
platform: "linux"
package: "curl"
version: "8.23.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_TFTP_BLKSIZE"
---

# CURLOPT\_TFTP\_BLKSIZE(3)

TFTP block size

## NAME

CURLOPT\_TFTP\_BLKSIZE - TFTP block size

## SYNOPSIS

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

## DESCRIPTION

Specify *blocksize* to use for TFTP data transmission. Valid range as per RFC 2348 is 8-65464 bytes. The default of 512 bytes is used if this option is not specified. The specified block size is only used if supported by the remote server. If the server does not return an option acknowledgment or returns an option acknowledgment with no block size, the default of 512 bytes is used.

## DEFAULT

512

## PROTOCOLS

This functionality affects tftp only

## EXAMPLE

```
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_URL, "tftp://example.com/bootimage");
    /* try using larger blocks */
    curl_easy_setopt(curl, CURLOPT_TFTP_BLKSIZE, 2048L);
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
```

## AVAILABILITY

Added in curl 7.19.4

## RETURN VALUE

*[curl\_easy\_setopt(3)](/curl_easy_setopt/3.md)* returns a CURLcode indicating success or error.

CURLE\_OK (0) means everything was OK, non-zero means an error occurred, see *[libcurl-errors(3)](/libcurl-errors/3.md)*.

## SEE ALSO

[**CURLOPT\_MAXFILESIZE**(3)](/CURLOPT_MAXFILESIZE/3.md)