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.TH CURLOPT_HSTS_CTRL 3 "September 06, 2021" "libcurl 7.83.1" "curl_easy_setopt options"

.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 will then automatically redirect 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
CURL *curl = curl_easy_init();
if(curl) {
  curl_easy_setopt(curl, CURLOPT_HSTS_CTRL, 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_HSTS "(3), " CURLOPT_CONNECT_TO "(3), " CURLOPT_RESOLVE "(3), "
.BR CURLOPT_ALTSVC "(3), "