What is difference between json-rpc and json-api?

Question

Could anybody explain advantage of using json-rpc over json-api and vice-versa? First and second format are JSON-based, but where I should use one, and where is another?

Answer 1

Note: I may come across a little biased. I am the author of the Json-RPC.net server library.

Json-RPC is a remote procedure call specification. There are multiple libraries you can use to communicate using that protocol. It is not REST based, and is transport agnostic. You can run it over HTTP as is very common, you can also use it over a socket, or any other transport you find appropriate. So it is quite flexible in that regard. You can also do server to client along with client to server requests with it by hosting the RPC server on either the client or the server.

Json-API is a specification for building REST APIs. There are multiple libraries you can use to get started with it. In contrast to Json-Rpc it requires you to host it on an HTTP server. You cannot invoke functions on the client with it. You cannot run it over a non-http transport protocol. Being REST based, it excels at providing information about Resources. If you want an API that is based around the idea of Create, Read, Update, Delete on some collections of resources, then this may be a good choice.

Json-API is going to be better if your API is resource-based, and you want your API to be browsable by a human without setting up documentation for it. Though that human would likely need to be in the software engineering field to make any sense of it.

Json-RPC is going to be better if your API is function based, or you want the flexibility it provides. Json-RPC can still be used to manipulate Resources by creating Create, Read, Update, and Delete functions for your resources, but you don't get the browsability with it not being REST based. It can still be explored (not browsed) by a human by generating documentation based off of the functions you expose.

A popular example of something that uses Json-Rpc is BitCoin.

There are a lot of popular REST-based API's and Json-API is a spec with a bunch of tools to help you do REST right.

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Note: Neither of those (Json-RPC, or Json-API) are good when you consider for developer time, performance, or efficiently using network resources.

If you care about performance, efficiency, or developer time then take a look at Google's gRPC which is fantastic in those regards, and can still reduce developer time more than using a REST API as client and server code can be generated from a protocol definition file.