Every protocol.
One place.

The most comprehensive, structured, and developer-friendly reference for communication protocols.

⌘K

1,000+

Protocols Documented

10,000+

Codes & Status Definitions

Layers of Coverage

Always

Free & Open for Everyone

5 LAYERS · 662+ PROTOCOLS · 10,000+ CODES · ALWAYS FREE

Quick lookups

View all

CodeStatusMeaningDefined InCommon In

100ContinueHTTP 100 Continue indicates the server has received the request headers and the client should proceed to send the request body.RFC 9110Large file uploads, APIs 101Switching ProtocolsHTTP 101 Switching Protocols indicates the server is switching to a different protocol as requested by the client via the Upgrade header.RFC 9110WebSocket upgrades 103Early HintsHTTP 103 Early Hints is an informational response that sends preliminary headers (typically Link preload directives) before the final response.RFC 8297CDNs, server-rendered web apps, performance optimization, edge networks 200OKHTTP 200 OK indicates the request has succeeded.RFC 9110All APIs, Browsers 201CreatedHTTP 201 Created indicates the request has been fulfilled and a new resource has been created.RFC 9110REST APIs 202AcceptedHTTP 202 Accepted indicates the request has been accepted for processing, but the processing has not been completed.RFC 9110Async APIs, job queues, batch processing 203Non-Authoritative InformationHTTP 203 Non-Authoritative Information means the request succeeded but the enclosed payload has been modified by a transforming proxy from the origin server's original 200 response.RFC 9110Transparent proxies, CDN edge transformations, content optimization gateways, mobile optimization proxies View all 65 HTTP status codes →

Popular lookups

View all

HTTP

HTTP 429

Too Many Requests

HTTP DNS

DNS MX

Mail Exchange Record

DNS TLS

TLS 1.3 Handshake

Transport Layer Security

TLS GRPC

gRPC Status Codes

Status Definitions

GRPC WEBSOCKET

WebSocket Close Codes

Close Event Codes

WEBSOCKET MCP

MCP Overview

Model Context Protocol

MCP

Protocol timeline

View timeline

1983TCP/IPRFC 793 1991HTTP 0.9RFC 1945 1997HTTP 1.1RFC 2616 2008TLS 1.2RFC 5246 2022HTTP 3RFC 9114 2024+MCPEmerging

Authoritative

Sourced from RFCs, specifications, and official documentation.

Structured

Every protocol follows the same clear, predictable structure.

Up to date

Continuously updated as standards evolve and new protocols emerge.

Open

Free to use, open to contribute, built for the engineering community.

Developer first

Examples, diagrams, and references designed for engineers.

Every protocol.One place.