These documents are Cloudflare’s interpretation of the Internet standards track protocol for HTTP response codes. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. We also included all of Cloudflare’s custom error codes (52x) and other commonly seen status codes.
In these articles we refer to the following terms quite a bit. To provide you with some content this is how we define the following:
Server - Any party receiving a request and sending a response. Either the origin or intermediate servers.
Origin/Host server - The final destination server. This server actually hosts the content of the website.
Proxy server - The server(s) that sit between the origin server and the client. Cloudflare is a proxy server for example.
Client - The party making the request. Typically an end user accessing the site on a browser, but may also be an API client or anyone requesting resources from the site.
Backend - The connections not made to or from the client, but between the proxy server(s) and/or the origin server
User-Agent - The machine used to send the request. Can be a browser or another program making requests (e.g. restful API requests)
Payload - the response or request data disincluding the headers. Also called response/request body
Note on Caching: Any HTTP status code that is cacheable by default will also be considered to be cacheable by Cloudflare (i.e., unless otherwise indicated by the method definition or explicit cache controls). Cloudflare caches HTTP responses similarly to how any request is cached. Cloudflare considers page rules, edge TTL, and origin headers when deciding whether to cache. For more information What Do I Tell Cloudflare What to Cache? and What does edge TTL mean?
HTTP Status Codes: