---
name: "CURLOPT_USERAGENT"
section: "3"
platform: "linux"
package: "curl"
version: "8.23.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_USERAGENT"
---

# CURLOPT\_USERAGENT(3)

HTTP user-agent header

## NAME

CURLOPT\_USERAGENT - HTTP user-agent header

## SYNOPSIS

```
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_USERAGENT, char *ua);
```

## DESCRIPTION

Pass a pointer to a null-terminated string as parameter. It is used to set the User-Agent: header field in the HTTP request sent to the remote server. You can also set any custom header with *[CURLOPT\_HTTPHEADER(3)](/CURLOPT_HTTPHEADER/3.md)*.

The application does not have to keep the string around after setting this option.

Using this option multiple times makes the last set string override the previous ones. Set it to NULL to disable its use again.

## DEFAULT

NULL, no User-Agent: header is used.

## PROTOCOLS

This functionality affects http only

## 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_USERAGENT, "Dark Secret Ninja/1.0");
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
```

## AVAILABILITY

Added in curl 7.1

## RETURN VALUE

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

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

## SEE ALSO

[**CURLOPT\_CUSTOMREQUEST**(3)](/CURLOPT_CUSTOMREQUEST/3.md), [**CURLOPT\_HTTPHEADER**(3)](/CURLOPT_HTTPHEADER/3.md), [**CURLOPT\_REFERER**(3)](/CURLOPT_REFERER/3.md), [**CURLOPT\_REQUEST\_TARGET**(3)](/CURLOPT_REQUEST_TARGET/3.md)