.\" generated by cd2nroff 0.1 from CURLOPT_HSTS_CTRL.md
.TH CURLOPT_HSTS_CTRL 3 "March 15 2024" libcurl
.SH NAME
CURLOPT_HSTS_CTRL \- control HSTS behavior
.SH SYNOPSIS
.nf
#include <curl/curl.h>

#define CURLHSTS_ENABLE       (1<<0)
#define CURLHSTS_READONLYFILE (1<<1)

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HSTS_CTRL, long bitmask);
.fi
.SH DESCRIPTION
HSTS (HTTP Strict Transport Security) means that an HTTPS server can instruct
the client to not contact it again over clear\-text HTTP for a certain period
into the future. libcurl then automatically redirects HTTP attempts to such
hosts to instead use HTTPS. This is done by libcurl retaining this knowledge
in an in\-memory cache.

Populate the long \fIbitmask\fP with the correct set of features to instruct
libcurl how to handle HSTS for the transfers using this handle.
.SH BITS
.IP CURLHSTS_ENABLE
Enable the in\-memory HSTS cache for this handle.
.IP CURLHSTS_READONLYFILE
Make the HSTS file (if specified) read\-only \- makes libcurl not save the cache
to the file when closing the handle.
.SH DEFAULT
0. HSTS is disabled by default.
.SH PROTOCOLS
HTTPS and HTTP
.SH EXAMPLE
.nf
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_HSTS_CTRL, (long)CURLHSTS_ENABLE);
    curl_easy_perform(curl);
  }
}
.fi
.SH AVAILABILITY
Added in 7.74.0
.SH RETURN VALUE
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
.SH SEE ALSO
.BR CURLOPT_ALTSVC (3),
.BR CURLOPT_CONNECT_TO (3),
.BR CURLOPT_HSTS (3),
.BR CURLOPT_RESOLVE (3)