401 Unauthorized - 10 Causes and How to Fix the HTTP 401 Error
Your request came back with 401 Unauthorized and nothing in the response body tells you why. Despite the name, 401 Unauthorized is not about permissions - it means the server could not authenticate you at all: the credentials were missing, malformed, expired, or meant for a different audience. That distinction matters because it cuts your search space in half. If you had been authenticated but lacked permission, you would be looking at 403 Forbidden instead. A 401 says the server does not know who you are. This page walks the ten causes that account for nearly every 401 in practice, most common first, each with a reproduction you can run and the exact lines that fix it. If your case does not match any of them, skip to the diagnostic checklist - it narrows an unknown 401 down in five steps. Error HTTP/1.1 401 Unauthorized WWW-Authenticate: Bearer realm="api", error="invalid_token" Where it happens Any HTTP client against any server - curl, fetch, axios, r...