Most public APIs you'll find in our directory are REST, but GraphQL and gRPC are common too, and each fits different problems. Here's a practical comparison.
At a glance
| REST | GraphQL | gRPC | |
|---|---|---|---|
| Transport | HTTP, JSON usually | HTTP, single endpoint, JSON | HTTP/2, Protocol Buffers (binary) |
| Contract | OpenAPI (optional) | Strongly typed schema | .proto files (required) |
| Client controls fields? | No (server decides) | Yes, exactly what it asks for | No (fixed messages) |
| Caching | Easy (HTTP caches, CDNs) | Harder (mostly POST, one URL) | Custom |
| Browser support | Native | Native | Needs gRPC-Web or a proxy |
| Streaming | Via SSE/WebSockets | Subscriptions | First-class, bidirectional |
| Best for | Public APIs, CRUD, cacheable data | Complex UIs with many related objects | Internal service-to-service calls, low latency |
REST
Resources live at URLs and are manipulated with HTTP methods (GET, POST, PUT, PATCH, DELETE). REST is easy to understand, works with every tool, and benefits from HTTP caching and status codes. The downsides are over-fetching (getting fields you don't need) and under-fetching (several calls to assemble one screen).
GraphQL
Clients send a query describing exactly the data they want, across related objects, and get it in one round trip. That's excellent for front-end teams iterating quickly. The costs are server complexity (resolvers, N+1 queries, query-cost limits for public APIs) and weaker HTTP caching.
gRPC
Services define methods and messages in Protocol Buffers, then generate typed clients in many languages. Binary encoding and HTTP/2 make it fast and compact, with built-in streaming. It shines between back-end services, but it's awkward for public web clients and harder to debug with everyday tools.
Also worth knowing
- Webhooks push events to you instead of you polling.
- Server-Sent Events / WebSockets keep a connection open for live updates.
- MCP exposes tools to AI agents. Many MCP servers wrap existing REST APIs.
Decision guide
- Building a public API for unknown developers? Start with REST + OpenAPI.
- Your own front end needs many related objects per screen, and you control the clients? Consider GraphQL.
- Internal microservices with high throughput or streaming needs? Choose gRPC.
- Want AI agents to use your product? Add an MCP server on top of whichever API you have.
Many mature platforms use more than one: gRPC internally, REST or GraphQL publicly, and webhooks for events.