Live demo

How APIs Talk

Every API is two boxes and a wire. What changes between protocols is who may speak first, how many trips the wire has to make, and what the bytes look like. Click through the tabs to fire real request shapes at a simulated server: watch REST over-fetch and stack up three sequential round trips, shape a GraphQL response field by field, multiplex unary and streaming gRPC calls over one HTTP/2 connection with real protobuf bytes on the wire, upgrade an HTTP request into a full-duplex WebSocket, and hold a single SSE response open while the server pushes status ticks and auto-reconnects after a drop. The final Race tab runs all five against the same errand on one clock. A runnable companion server and client for every scenario lives at github.com/sacredvoid/api-protocol-playground.