CURLOPT_SSL_FALSESTART(3) Library Functions Manual CURLOPT_SSL_FALSESTART(3)
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
This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS,
POP3S, SMTPS etc.
No TLS backend supports this option.
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);
}
}
DEPRECATED
Deprecated since 8.15.0.
AVAILABILITY
Added in curl 7.42.0
RETURN VALUE
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).
SEE ALSO
CURLOPT_TCP_FASTOPEN(3)
libcurl 2026-03-23 CURLOPT_SSL_FALSESTART(3)
curl 8.19.0 - Generated Tue Mar 31 13:26:26 CDT 2026