CURLOPT_USERNAME(3)

💅 CURLOPT_USERNAME 💅

okay so real talk, this is the <curl/curl.h> girlie whose whole job is telling curl who you are when a server asks. it lives in the Library Functions Manual, and honestly? iconic behavior. ✨

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🌸 NAME 🌸

CURLOPT_USERNAME — the username to use in authentication 🫶

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✨ SYNOPSIS ✨

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_USERNAME,
                          char *username);

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🎀 DESCRIPTION 🎀

so you pass a char pointer as the parameter, and that pointer should point to a null-terminated username — like, the actual username you wanna use for the transfer. simple as that, no cap. 💖

CURLOPT_USERNAME(3) sets the username that gets used in protocol authentication. and bestie, listen: you should not use this option together with the older CURLOPT_USERPWD(3) option. pick one, ok? don't be messy. 🙈

now for the ✨situations✨:

• if you're doing Kerberos V5 authentication against a Windows based server, you should include the domain name so the server can successfully obtain a Kerberos Ticket. skip it and the initial part of the authentication handshake may fail. 💀 like literally, it'll just not work.
• if you're using NTLM, you can just specify the username plain, no domain name, should the server be part of a single domain and forest. easy. 🌸
• wanna include the domain name? use either Down-Level Logon Name or UPN (User Principal Name) formats. for example, EXAMPLEser and user@example.com respectively. 🦋
• some HTTP servers (on Windows) support inclusion of the domain for Basic authentication as well. cute of them honestly. ✨

and if you also need the password and login options along with the username? that's what CURLOPT_PASSWORD(3) and CURLOPT_LOGIN_OPTIONS(3) are for. the whole friend group fr fr. 👑

good news for your memory management anxiety: the application does not have to keep the string around after setting this option. curl handles it. you're free. 🕊️

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🦋 DEFAULT 🦋

blank 🫥

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👑 PROTOCOLS 👑

this functionality affects all supported protocols. all of them. every single one. main character energy tbh. 🌈

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💜 EXAMPLE 💜

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/foo.bin");

    curl_easy_setopt(curl, CURLOPT_USERNAME, "clark");

    result = curl_easy_perform(curl);

    curl_easy_cleanup(curl);
  }
}

look at clark go. we love a named user 🥹💫

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🌟 AVAILABILITY 🌟

added in curl 7.19.1 — a whole era ✨

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🔥 RETURN VALUE 🔥

curl_easy_setopt(3) returns a CURLcode indicating success or error. bestie breakdown:

• CURLE_OK (0) means everything was OK 💚
• non-zero means an error occurred 😭 — go check libcurl-errors(3)

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🍓 SEE ALSO 🍓

• CURLOPT_HTTPAUTH(3)
• CURLOPT_PASSWORD(3)
• CURLOPT_PROXYAUTH(3)
• CURLOPT_USERPWD(3)

go read them, they're all part of the same squad 🫶

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and that's the page, bestie!! brought to you by libcurl, dated 2026-10-12 — mwah, go authenticate something cute 💅✨