.\" generated by cd2nroff 0.1 from CURLOPT_HSTSREADDATA.md
.TH CURLOPT_HSTSREADDATA 3 "2026-09-02" libcurl
.SH NAME
CURLOPT_HSTSREADDATA \- pointer passed to the HSTS read callback
.SH SYNOPSIS
.nf
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HSTSREADDATA, void *pointer);
.fi
.SH DESCRIPTION
Data \fIpointer\fP to pass to the HSTS read function. If you use the
\fICURLOPT_HSTSREADFUNCTION(3)\fP option, this is the pointer you get as input
in the 3rd argument to the callback.

This option does not enable HSTS, you need to use \fICURLOPT_HSTS_CTRL(3)\fP to
do that.
.SH DEFAULT
NULL
.SH PROTOCOLS
This functionality affects http only
.SH EXAMPLE
.nf
struct MyData {
  void *custom;
};

static CURLSTScode hsts_cb(CURL *easy, struct curl_hstsentry *sts,
                           void *clientp)
{
  /* populate the struct as documented */
  return CURLSTS_OK;
}

int main(void)
{
  CURL *curl = curl_easy_init();
  struct MyData my_data;
  if(curl) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");

    /* pass pointer that gets passed in to the
       CURLOPT_HSTSREADFUNCTION callback */
    curl_easy_setopt(curl, CURLOPT_HSTSREADDATA, &my_data);
    /* set HSTS read callback */
    curl_easy_setopt(curl, CURLOPT_HSTSREADFUNCTION, hsts_cb);

    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
.fi
.SH AVAILABILITY
Added in curl 7.74.0
.SH RETURN VALUE
This returns CURLE_OK.
.SH SEE ALSO
.BR CURLOPT_HSTS (3),
.BR CURLOPT_HSTSREADFUNCTION (3),
.BR CURLOPT_HSTSWRITEDATA (3),
.BR CURLOPT_HSTSWRITEFUNCTION (3)