CURLOPT_HTTP09_ALLOWED(3)

📦
version 8.18.0 · 24 versions
, in fedora 44

💅 CURLOPT_HTTP09_ALLOWED(3) — the libcurl manual page, but make it make sense

okay bestie so we're in the CURLOPT_HTTP09_ALLOWED(3) page from the Library Functions Manual, and honestly? this one is a lil niche but it's giving "important safety girl" energy, so let's get into it 🎀

✨ NAME ✨

CURLOPT_HTTP09_ALLOWED — the option that decides whether you're allowed to accept an HTTP/0.9 response 💖

🌸 SYNOPSIS 🌸

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTP09_ALLOWED, long allowed);

like yes, that's the whole vibe. one curl_easy_setopt call, one long, we move 🫶

🦋 DESCRIPTION 🦋

so here's the tea ☕ — you pass the long argument allowed and you set it to 1L if you want to allow HTTP/0.9 responses. that's literally it. 1L = permission granted, bestie 💅

and what even is an HTTP/0.9 response, you ask? okay so it's a server response that's entirely without headers and only a body. no header section, no little metadata moment, just vibes and a body. iconic in a chaotic way ngl.

here's the part where u need to be a little careful tho 😭 — you can connect to lots of random TCP services and still get a response that curl might consider to be HTTP/0.9. like, anything on the internet could look like HTTP/0.9 to curl if you're not paying attention. so this option is lowkey a "do I trust this rando" switch. be mindful ✨

💜 DEFAULT 💜

0

yup. off by default. not allowed unless u say so. the safe girlie default 💖

🌈 PROTOCOLS 🌈

this functionality affects http only — that's the whole list, no cap 🫶

🔥 EXAMPLE 🔥

here's the lil code moment, copied exactly because we do not freestyle the code:

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

see that CURLOPT_HTTP09_ALLOWED, 1L? that's the star of the show, main character energy fr fr 👑

🧚 HISTORY 🧚

okay so storytime 📖 — curl allowed HTTP/0.9 responses by default before 7.66.0. wild, I know. the old days were just different.

then since 7.66.0, libcurl requires this option set to 1L to allow HTTP/0.9 responses. so now it's opt-in only. the glow-up was real 💅

⭐ AVAILABILITY ⭐

Added in curl 7.64.0 — so if ur on something ancient, this option isn't gonna be there for u, and that's just how it is 😭

🍓 RETURN VALUE 🍓

curl_easy_setopt(3) returns a CURLcode indicating success or error. cute and simple.

  • CURLE_OK (0) means everything was OK — slay ✨
  • non-zero means an error occurred — not slay 💀

if u get the non-zero situation, go see libcurl-errors(3) for the full breakdown.

💀 SEE ALSO 💀

go read those if u wanna keep the rabbit hole going, iykyk 🐇

lowkey reminder: allowing HTTP/0.9 means accepting responses with no headers at all, and random TCP services can totally produce stuff curl might read as HTTP/0.9. default is 0 for a reason, bestie 🙈

and that's the page!! tysm for reading, ur doing amazing sweetie 🫶 this was libcurl, dated 2026-10-12, and the page is CURLOPT_HTTP09_ALLOWED(3) — mwah 💋✨

📦 where this page comes from