The client must authenticate with the proxy; the Proxy-Authenticate header explains how.
Quick facts
When does it occur
The client must authenticate with the proxy; the Proxy-Authenticate header explains how.
It belongs to the 4xx Client Error class of responses, defined in RFC7235#3.2.
Browse all codes in this class: 4xx Client Error
Common causes
Frequently asked questions
407 belongs to the 4xx Client Error class and is generally not cached for long; behavior is controlled by Cache-Control.
4xx Client Error: The client must authenticate with the proxy; the Proxy-Authenticate header explains how.
Sources & standards
Updated 2026-09-13
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