CURLOPT\_HTTP09\_ALLOWED(3) Library Functions Manual CURLOPT\_HTTP09\_ALLOWED(3)

# [NAME](#NAME)

CURLOPT\_HTTP09\_ALLOWED - allow HTTP/0.9 response

# [SYNOPSIS](#SYNOPSIS)

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

# [DESCRIPTION](#DESCRIPTION)

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.

# [DEFAULT](#DEFAULT)

0

# [PROTOCOLS](#PROTOCOLS)

This functionality affects http only

# [EXAMPLE](#EXAMPLE)

```
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);


  }
}
```

# [HISTORY](#HISTORY)

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.

# [AVAILABILITY](#AVAILABILITY)

Added in curl 7.64.0

# [RETURN VALUE](#RETURN_VALUE)

[*curl\_easy\_setopt(3)*](/man/os/curl/curl_easy_setopt.3) returns a CURLcode indicating success or error.

CURLE\_OK (0) means everything was OK, non-zero means an error occurred, see [*libcurl-errors(3)*](/man/os/curl/libcurl-errors.3).

# [SEE ALSO](#SEE_ALSO)

[**CURLOPT\_HTTP\_VERSION**(3)](/man/os/curl/CURLOPT_HTTP_VERSION.3), [**CURLOPT\_SSLVERSION**(3)](/man/os/curl/CURLOPT_SSLVERSION.3)

2026-10-31 libcurl

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Document: CURLOPT_HTTP09_ALLOWED(3) from curl 8.23.0-r3 (Chainguard OS)
Source: https://github.com/curl/curl.git