Browse by Protocol
Hypertext Transfer Protocol
The foundation of data communication on the web. HTTP status codes indicate the result of a client's request to a …
Simple Mail Transfer Protocol
The standard protocol for sending email across the Internet. SMTP reply codes indicate the success or failure of mail transactions.
gRPC Remote Procedure Call
A high-performance RPC framework by Google. gRPC status codes describe the outcome of remote procedure calls.
Domain Name System
The hierarchical naming system for computers and services on the Internet. DNS response codes (RCODEs) indicate query results.
WebSocket Protocol
A protocol providing full-duplex communication channels over a single TCP connection. Close codes indicate why a connection was terminated.
File Transfer Protocol
A standard protocol for transferring files between a client and server. FTP reply codes indicate the status of file transfer …
Session Initiation Protocol
A signaling protocol for initiating, maintaining, and terminating multimedia sessions. SIP response codes follow a structure similar to HTTP.
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Comparisons
Side-by-side comparisons of commonly confused status codes.
41 comparisonsGlossary
Technical terms and concepts for protocols and networking.
360 termsGuides
How-to articles on debugging, caching, security, and more.
172 guidesTools
Interactive tools for headers, status codes, and mock responses.
4 tools