HTTP delivery
HTTP 401: an authentication challenge, explained
An HTTP 401 response means that the requested resource requires authentication that the server has not accepted for that request.
Read the guideGuides & directories
Learn about networks, accounts and viewing
Use practical technical references to understand a connection, message or account decision.
82 guides · Page 1 of 4
HTTP delivery
HTTP 403: when a server refuses a request
HTTP 403 means that a server understood a request and refused it.
Read the guideHTTP delivery
HTTP 404: distinguish a missing address from a broken account
HTTP 404 means the server did not provide a current representation at the requested address, or is unwilling to disclose that one exists.
Read the guideHTTP delivery
HTTP 410: a resource marked as gone
HTTP 410 tells a client that the requested resource is no longer available and that the condition is likely to be permanent.
Read the guideHTTP delivery
HTTP 429: stop a retry loop before it grows
HTTP 429 means that too many requests have been made within the server's counting policy.
Read the guideHTTP delivery
HTTP 500: preserve the action that triggered the server fault
HTTP 500 reports that the server encountered an unexpected condition while handling a request.
Read the guideHTTP delivery
HTTP 502: a gateway received an invalid upstream response
HTTP 502 means that a server acting as a gateway or proxy received an invalid response from an upstream server.
Read the guideHTTP delivery
HTTP 503: temporary unavailability and a sensible retry
HTTP 503 indicates that a server is not currently ready to handle the request.
Read the guideHTTP delivery
HTTP 504: when an upstream reply arrives too late
HTTP 504 means that a gateway or proxy did not receive an upstream response in time.
Read the guideHTTP delivery
HTTP 206: successful partial content, not a partial subscription
HTTP 206 is a successful response that supplies part of a resource requested through a range request.
Read the guideHTTP delivery
HTTP 304: using a stored response after validation
HTTP 304 tells a client that a conditionally requested representation has not changed, so the client can use its stored copy.
Read the guideHTTP delivery
HTTP 416: when a requested media range does not fit
HTTP 416 means a server cannot satisfy the requested range for the selected resource.
Read the guideHTTP delivery
Streaming redirects: follow the destination without losing trust
An HTTP redirect sends a client to another address.
Read the guideHTTP delivery
Signed media URLs: expiry is different from account expiry
A signed media URL can carry time-limited authorization for a resource.
Read the guideHTTP delivery
HTTP response or connection failure: identify which one happened
An HTTP response means an HTTP-speaking server or intermediary returned a response.
Read the guideHTTP delivery
Retry-After: read a waiting instruction correctly
Retry-After is an HTTP response header that tells a client when to make a later request.
Read the guideHTTP delivery
Private caching: what no-store and private actually mean
Cache-Control directs HTTP caching behaviour.
Read the guideHTTP delivery
Content-Type: a successful download can still be the wrong thing
Content-Type describes the media type of a response.
Read the guideHTTP delivery
CORS: a browser permission boundary, not a broadband fault
Cross-Origin Resource Sharing, or CORS, is a browser mechanism controlling whether a web page can read certain responses from another origin.
Read the guideHome networking
NXDOMAIN: when the requested hostname does not exist
NXDOMAIN is a DNS answer saying that the queried domain name does not exist.
Read the guideHome networking
Negative DNS caching: why a corrected name may still fail
A resolver can retain a previous answer that a DNS name does not exist.
Read the guideHome networking
DNS TTL: a cache lifetime, not a video buffer
A DNS time to live, or TTL, tells a resolver how long it may cache a DNS record.
Read the guideHome networking
DNS resolver and authoritative server: who answers which question?
A recursive resolver looks up names for a client and can cache the answers.
Read the guideHome networking
Private and public IP addresses in a home streaming setup
A private IPv4 address identifies a device within an applicable private network.
Read the guide