---
name: "CURLOPT_SSL_FALSESTART"
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_SSL_FALSESTART"
---

# CURLOPT\_SSL\_FALSESTART(3)

TLS false start

## NAME

CURLOPT\_SSL\_FALSESTART - TLS false start

## SYNOPSIS

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

## DESCRIPTION

Pass a long as parameter set to 1L to enable or 0 to disable.

This option determines whether libcurl should use false start during the TLS handshake. False start is a mode where a TLS client starts sending application data before verifying the server's Finished message, thus saving a round trip when performing a full handshake.

## DEFAULT

0

## PROTOCOLS

All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

## EXAMPLE

```
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
    curl_easy_setopt(curl, CURLOPT_SSL_FALSESTART, 1L);
    curl_easy_perform(curl);
  }
}
```

## AVAILABILITY

Added in 7.42.0. This option is currently only supported by the Secure Transport (on iOS 7.0 or later, or OS X 10.9 or later) TLS backend.

## RETURN VALUE

Returns CURLE\_OK if false start is supported by the SSL backend, otherwise returns CURLE\_NOT\_BUILT\_IN.

## SEE ALSO

[**CURLOPT\_TCP\_FASTOPEN**(3)](/CURLOPT_TCP_FASTOPEN/3.md)