The most obvious time you'd encounter a 401 error, on the other hand, is when you have not logged in at all, or have provided the incorrect password.

The server generating a 401 response MUST send a WWW-Authenticate header field (Section 4.1) containing at least one challenge applicable to the target resource.

Authentication by schemes outside of RFC2617 is not supported in HTTP status codes and are not considered when deciding whether to use 401 or 403.

Meaning if you have your own roll-your-own login process and never use HTTP Authentication, 403 is always the proper response and 401 should never be used.

If HTTP authentication is not in use and the service has a cookie-based authentication scheme as is the norm nowadays, then a 403 or a 404 should be returned.

The statement is "If the request already included Authorization credentials". That means if this is a response from a request which provided the credential (e.g. the response from a RFC2617 Authentication attempt). It is essentially to allow the server to say, "Bad account/password pair, try again". In the posed question, the user is presumably authenticated but not authorized. 401 is never the appropriate response for those circumstances.

401 is only appropriate for HTTP Authentication

I'm using both - the 401 for unauthenticated users, the 403 for authenticated users with insufficient permissions.

From your use case, it appears that the user is not authenticated. I would return 401.

There's a problem with 401 Unauthorized, the HTTP status code for authentication errors. And that’s just it: it’s for authentication, not authorization. Receiving a 401 response is the server telling you, “you aren’t authenticated–either not authenticated at all or authenticated incorrectly–but please reauthenticate and try again.” To help you out, it will always include a WWW-Authenticate header that describes how to authenticate.

So, for authorization I use the 403 Forbidden response. It’s permanent, it’s tied to my application logic, and it’s a more concrete response than a 401. Receiving a 403 response is the server telling you, “I’m sorry. I know who you are–I believe who you say you are–but you just don’t have permission to access this resource. Maybe if you ask the system administrator nicely, you’ll get permission. But please don’t bother me again until your predicament changes.”

401 'Unauthorized' should be 401 'Unauthenticated', problem solved !

UNAUTHORIZED: Status code (401) indicating that the request requires authentication, usually this means user needs to be logged-in (session). User/agent unknown by the server. Can repeat with other credentials. NOTE: This is confusing as this should have been named 'unauthenticated' instead of 'unauthorized'.

+----------------------- | RESOURCE EXISTS ? (if private it is often checked AFTER auth check) +----------------------- | | NO | v YES v +----------------------- 404 | IS LOGGED-IN ? (authenticated, aka user session) or +----------------------- 401 | | 403 NO | | YES 3xx v v 401 +----------------------- (404 no reveal) | CAN ACCESS RESOURCE ? (permission, authorized, ...) or +----------------------- redirect | | to login NO | | YES | | v v 403 OK 200, redirect, ... (or 404: no reveal) (or 404: resource does not exist if private) (or 3xx: redirection)

I would expect that 401 to be named "Unauthenticated" and 403 to be named "Unauthorized". It is very confusing that 401, which has to do with Authentication,

The server generating a 401 response MUST send a WWW-Authenticate header field (Section 4.1) containing at least one challenge applicable to the target resource.

If the ticket is incorrect or damaged, you cannot even go through the airport security: when they check your ticket, it will be refused. You are Forbidden to enter the boarding area of the airport.

These two sound pretty similar to me. And to make things even more confusing, 403 “Forbidden” says that the server refuses to “authorize” the request but it’s code 401 that is called “Unauthorized”. 😵

Indicates that though the request was valid, the server refuses to respond to it. Unlike the 401 status code, providing authentication will not change the outcome.

401 Unauthorized The requestor is not authorized to access the resource. This is similar to 402 but is used in cases where authentication is expected but has failed or has not been provided.

401 :unauthorized

You’d like to access the content of the resource but you’re not logged in (so not authenticated yet). The server will return you a 401 error. You need to log in to be able to access the resource.

Handling 401s well is important for the user's experience. They won't happen often (though more often than I expected), but really do break everything if you're not careful. Getting a good authentication abstraction library for Vue or Ember or whatever you are using should help with a lot of the boring parts. You'll probably need to define some extra strategies/rules for this cookie session approach, but if it's anything like in ember-simple-auth they're so simple it feels like cheating, because the Rails app is doing all of the hard work and you just need the js part to spot a 401 and handle logging in and retrying whatever it was doing before.

This status is sent with a WWW-Authenticate header that contains information on how to authorize correctly.

The HTTP 401 Unauthorized client error status response code indicates that the request has not been applied because it lacks valid authentication credentials for the target resource.

Similar to 403 Forbidden, but specifically for use when authentication is required and has failed or has not yet been provided. The response must include a WWW-Authenticate header field containing a challenge applicable to the requested resource.