CURLOPT_FOLLOWLOCATION(3) Library Functions Manual CURLOPT_FOLLOWLOCATION(3)

CURLOPT_FOLLOWLOCATION - follow HTTP 3xx redirects

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

A long parameter set to 1 tells the library to follow any Location: header redirects that an HTTP server sends in a 30x response. The Location: header can specify a relative or an absolute URL to follow.

libcurl issues another request for the new URL and follows subsequent new Location: redirects all the way until no more such headers are returned or the maximum limit is reached. CURLOPT_MAXREDIRS(3) is used to limit the number of redirects libcurl follows.

libcurl restricts what protocols it automatically follow redirects to. The accepted target protocols are set with CURLOPT_REDIR_PROTOCOLS(3). By default libcurl allows HTTP, HTTPS, FTP and FTPS on redirects.

When following a redirect, the specific 30x response code also dictates which request method libcurl uses in the subsequent request: For 301, 302 and 303 responses libcurl switches method from POST to GET unless CURLOPT_POSTREDIR(3) instructs libcurl otherwise. All other redirect response codes make libcurl use the same method again.

For users who think the existing location following is too naive, too simple or just lacks features, it is easy to instead implement your own redirect follow logic with the use of curl_easy_getinfo(3)'s CURLINFO_REDIRECT_URL(3) option instead of using CURLOPT_FOLLOWLOCATION(3).

Since libcurl changes method or not based on the specific HTTP response code, setting CURLOPT_CUSTOMREQUEST(3) while following redirects may change what libcurl would otherwise do and if not that carefully may even make it misbehave since CURLOPT_CUSTOMREQUEST(3) overrides the method libcurl would otherwise select internally.

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HTTP

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
    /* example.com is redirected, so we tell libcurl to follow redirection */
    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
    curl_easy_perform(curl);
  }
}

Along with HTTP

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

CURLINFO_REDIRECT_COUNT(3), CURLINFO_REDIRECT_URL(3), CURLOPT_POSTREDIR(3), CURLOPT_PROTOCOLS(3), CURLOPT_REDIR_PROTOCOLS(3)

2024-05-22 libcurl