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Jun 23, 2026
4xx Client Error
The 407 (Proxy Authentication Required) status code is similar to 401 but indicates that the client must authenticate with a proxy server. The response must include a Proxy-Authenticate header field containing a challenge applicable to the proxy.
When deploying applications in a corporate environment, clients may receive 407 when trying to access external APIs through a corporate proxy. Configure the HTTP client to send Proxy-Authorization credentials or configure system-wide proxy settings.
// PHP - cURL with proxy authentication
curl_setopt_array($ch, [
CURLOPT_PROXY => 'http://proxy.company.com:8080',
CURLOPT_PROXYUSERPWD => 'username:password',
CURLOPT_PROXYAUTH => CURLAUTH_BASIC,
]);
Mistake: Using 401 instead of 407 for proxy authentication
Fix: If the authentication is required by a proxy (not the origin server), use 407 with a Proxy-Authenticate header. 401 is for origin server authentication.
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