CURLOPT\_SSL\_FALSESTART(3) Library Functions Manual CURLOPT\_SSL\_FALSESTART(3)

# [NAME](#NAME)

CURLOPT\_SSL\_FALSESTART - TLS false start

# [SYNOPSIS](#SYNOPSIS)

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

# [DESCRIPTION](#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](#DEFAULT)

0

# [PROTOCOLS](#PROTOCOLS)

This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc. only

No TLS backend supports this option.

# [EXAMPLE](#EXAMPLE)

```
int main(void)
{


  CURL *curl = curl_easy_init();


  if(curl) {


    CURLcode result;


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


    curl_easy_setopt(curl, CURLOPT_SSL_FALSESTART, 1L);


    result = curl_easy_perform(curl);


    curl_easy_cleanup(curl);


  }
}
```

# [DEPRECATED](#DEPRECATED)

Deprecated since 8.15.0.

# [AVAILABILITY](#AVAILABILITY)

Added in curl 7.42.0

# [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\_TCP\_FASTOPEN**(3)](/man/os/curl/CURLOPT_TCP_FASTOPEN.3)

2026-10-14 libcurl

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Document: CURLOPT_SSL_FALSESTART(3) from curl 8.23.0-r0 (Chainguard OS)
Source: https://github.com/curl/curl.git