CURLOPT_USERAGENT(3)

💅 CURLOPT_USERAGENT(3) — like, the HTTP user-agent header one

okay bestie, so this is a page from the Library Functions Manual (libcurl girlies rise 🫶) and it's all about telling the internet who you are. or, y'know, who you're pretending to be. main character energy fr fr ✨

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🌸 NAME 🌸

CURLOPT_USERAGENT — the HTTP user-agent header, and yes it's exactly as iconic as it sounds 💅

✨ SYNOPSIS ✨

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_USERAGENT, char *ua);

💖 DESCRIPTION 💖

So basically 🎀 you pass a pointer to a null-terminated string as the parameter, and that string becomes the User-Agent: header field in the HTTP request that gets sent to the remote server. That's it. That's the whole vibe check. It's literally just you announcing yourself to the server. 🌈

And ngl, if you want to set any other custom header too, you can do that with CURLOPT_HTTPHEADER(3) — this option is just the dedicated one for user-agent, iykyk. 👑

The good news? The application does not have to keep the string around after setting this option. Set it and forget it, bestie, curl's got it from there 💜

Also, small but important: using this option multiple times makes the last set string override all the previous ones. And if you set it to NULL, you disable its use again — like, back to being a mystery to the server 🙈

🦋 DEFAULT 🦋

NULL — like, no User-Agent: header is used at all. you're a ghost, a rumour, a vibe with no name 💀

🍓 PROTOCOLS 🍓

This functionality affects http only — that's it, that's the list, no cap 🎯

🔥 EXAMPLE 🔥

okay here's the whole thing, exactly as written, copy it and slay:

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

    curl_easy_setopt(curl, CURLOPT_USERAGENT, "Dark Secret Ninja/1.0");

    curl_easy_perform(curl);
  }
}

"Dark Secret Ninja/1.0" — genuinely iconic string choice, whoever picked it ate and left no crumbs 😭🔥

⭐ AVAILABILITY ⭐

Added in curl 7.1 — ancient, vintage, elder-gen Z of curl versions, we respect her 🎀

🌸 RETURN VALUE 🌸

curl_easy_setopt(3) returns a CURLcode indicating success or error — that's your vibe report card 🫶

CURLE_OK (0) means everything was OK. non-zero means an error occurred, so go check libcurl-errors(3) — she'll tell you what went wrong 👑

💫 SEE ALSO 💫

• CURLOPT_CUSTOMREQUEST(3)
• CURLOPT_HTTPHEADER(3)
• CURLOPT_REFERER(3)
• CURLOPT_REQUEST_TARGET(3)

Go read those too, they're all in the same friend group 💖

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✨ that's a wrap bestie ✨ this little cutie is a libcurl page, dated 2026-10-12, and it lives with the rest of the CURLOPT_USERAGENT(3) lore. mwah 💋 go set a user-agent that's as extra as you are 🦋