.\" generated by cd2nroff 0.1 from CURLOPT_HSTS_CTRL.md
.TH CURLOPT_HSTS_CTRL 3 "2024-11-07" 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
.SH PROTOCOLS
This functionality affects http only
.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 curl 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)