---
name: "CURLOPT_BUFFERSIZE"
section: "3"
platform: "macos"
package: "curl"
version: "166.0.0.0.1"
release: "macOS 26.5"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_BUFFERSIZE"
---

# CURLOPT\_BUFFERSIZE(3)

receive buffer size

## NAME

CURLOPT\_BUFFERSIZE - receive buffer size

## SYNOPSIS

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

## DESCRIPTION

Pass a long specifying your preferred *size* (in bytes) for the receive buffer in libcurl. The main point of this would be that the write callback gets called more often and with smaller chunks. Secondly, for some protocols, there is a benefit of having a larger buffer for performance.

This is just treated as a request, not an order. You cannot be guaranteed to actually get the given size.

This buffer size is by default *CURL\_MAX\_WRITE\_SIZE* (16kB). The maximum buffer size allowed to be set is *CURL\_MAX\_READ\_SIZE* (10MB). The minimum buffer size allowed to be set is 1024.

DO NOT set this option on a handle that is currently used for an active transfer as that may lead to unintended consequences.

The maximum size was 512kB until 7.88.0.

## DEFAULT

CURL\_MAX\_WRITE\_SIZE (16kB)

## PROTOCOLS

All

## EXAMPLE

```
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    curl_easy_setopt(curl, CURLOPT_URL, "sftp://example.com/foo.bin");
    /* ask libcurl to allocate a larger receive buffer */
    curl_easy_setopt(curl, CURLOPT_BUFFERSIZE, 120000L);
    res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
```

## AVAILABILITY

Added in 7.10. Growing the buffer was added in 7.53.0.

## RETURN VALUE

Returns CURLE\_OK if the option is supported, and CURLE\_UNKNOWN\_OPTION if not.

## SEE ALSO

[**CURLOPT\_MAXFILESIZE**(3)](/CURLOPT_MAXFILESIZE/3.md), [**CURLOPT\_MAX\_RECV\_SPEED\_LARGE**(3)](/CURLOPT_MAX_RECV_SPEED_LARGE/3.md), [**CURLOPT\_UPLOAD\_BUFFERSIZE**(3)](/CURLOPT_UPLOAD_BUFFERSIZE/3.md), [**CURLOPT\_WRITEFUNCTION**(3)](/CURLOPT_WRITEFUNCTION/3.md)