407 Proxy Authentication Required is similar to 401, but it is a proxy, not the origin server, that requires the client to authenticate. The proxy must send a Proxy-Authenticate header with a challenge, and the client then repeats the request with a Proxy-Authorization header.
It occurs in company and school networks with authenticating forward proxies and with commercial proxy services that require a username and password. Browsers show a proxy login prompt; command-line tools need the proxy credentials configured, for example with curl --proxy-user.
Example response
HTTP/1.1 407 Proxy Authentication Required
Date: Fri, 06 Nov 2026 10:15:32 GMT
Proxy-Authenticate: Basic realm="Corporate proxy"
Content-Length: 0SEO and redirect checking
Origin servers do not send 407 to search engines unless they are configured as a proxy, so it has no direct SEO impact. TrueURL checks run in Cloudflare's network without a proxy in between, so a 407 in a result means the target itself behaves like an authenticating proxy.
Common causes and use cases
- A company proxy requires sign-in before it allows web access.
- A paid proxy service rejects requests without valid credentials.
- A change in proxy configuration means that applications no longer send their proxy credentials.