CURLOPT_HTTP09_ALLOWED(3) Library Functions Manual CURLOPT_HTTP09_ALLOWED(3)

CURLOPT_HTTP09_ALLOWED - allow HTTP/0.9 response

#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTP09_ALLOWED, long allowed);

Pass the long argument allowed set to 1L to allow HTTP/0.9 responses.

An HTTP/0.9 response is a server response entirely without headers and only a body. You can connect to lots of random TCP services and still get a response that curl might consider to be HTTP/0.9!

curl allowed HTTP/0.9 responses by default before 7.66.0

Since 7.66.0, libcurl requires this option set to 1L to allow HTTP/0.9 responses.

HTTP

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode ret;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
    curl_easy_setopt(curl, CURLOPT_HTTP09_ALLOWED, 1L);
    ret = curl_easy_perform(curl);
  }
}

Option added in 7.64.0, present along with HTTP.

Returns CURLE_OK if HTTP is supported, and CURLE_UNKNOWN_OPTION if not.

CURLOPT_HTTP_VERSION(3), CURLOPT_SSLVERSION(3)

2024-05-22 libcurl