CURLOPT_HSTSWRITEDATA(3)

💅 CURLOPT_HSTSWRITEDATA(3) 💅

okay so bestie, welcome to the CURLOPT_HSTSWRITEDATA page from the libcurl Library Functions Manual ✨ this one is short, sweet, and extremely “pass the pointer, bestie” energy.

🌸 NAME 🌸

CURLOPT_HSTSWRITEDATA — pointer passed to the HSTS write callback 💫

🦋 SYNOPSIS 🦋

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HSTSWRITEDATA, void *pointer);

💖 DESCRIPTION 💖

It’s the data pointer to pass to the HSTS write function, bestie. If you’re using the CURLOPT_HSTSWRITEFUNCTION(3) option, this is literally the pointer you get as input in the fourth argument to the callback 🫶

⚠️ ok important: this option does not enable HSTS. You need to use CURLOPT_HSTS_CTRL(3) to do that. no cap, don’t forget it 💀

🎀 DEFAULT 🎀

• NULL — that’s the whole default, bestie 🕳️

🌈 PROTOCOLS 🌈

• This functionality affects http only 🦋

✨ EXAMPLE ✨

struct MyData {
  void *custom;
};

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

    /* pass pointer that gets passed in to the
       CURLOPT_HSTSWRITEFUNCTION callback */
    curl_easy_setopt(curl, CURLOPT_HSTSWRITEDATA, &this);

    curl_easy_perform(curl);
  }
}

🔥 AVAILABILITY 🔥

• Added in curl 7.74.0 🎀

👑 RETURN VALUE 👑

• This returns CURLE_OK 👑 that’s it, that’s the vibe.

🫶 SEE ALSO 🫶

• CURLOPT_HSTS(3)
• CURLOPT_HSTSREADDATA(3)
• CURLOPT_HSTSREADFUNCTION(3)
• CURLOPT_HSTSWRITEFUNCTION(3)

---

later, bestie 🫶 — this page came from libcurl and is dated 2026-10-12. mwah 💋