What is difference between "Rest" API and "Graph" API

Question

I am creating an API project in Azure AD B2C in which I want to create a custom UI. For this requirement, I want to know which is better in both "Rest" API & "Graph" API.

Can anyone suggest to me, which is better to use?

Answer 1

While GraphQL is often mentioned as the replacement for REST, both tackle different problems actually.

REST, to start with, is not a protocol but just a style, which, if applied correctly, just decouples clients from servers. A server following the REST principals will therefore provide the client with any information needed to take further steps. A client initially starts without any a-priori knowledge and learns on the fly through issuing requests and processing responses.

While REST is protocol agnostic, meaning it can be build up ontop of many protocols, HTTP is probably the most prominent one. A common sample for a RESTful client is the Web browser we are all to familiar with. It will start by invoking either a bookmarked URI or invoke one entered in the address bar and progress from there on.

HTTP doesn't specify the representation the request or response has to be sent in but leaves that to clients and servers negotiating them. This helps in decoupling as both client and servers can rely on the common interface (HTTP) and only bind strongly onto the known media types used to exchange data in. A peer not being able to process a document in a certain representation (due to the lack of the respective mime type support) will indicate his other peer via a respective error message. The media type, which is just a human readable documentation of the syntax and the semantics of the data payload, is therefore the most important part in a REST architecture. It teaches a peer how to parse and interpret the received payload and to actually make sense out of it, though plenty of people still confuse REST for a JSON based HTTP API with over-engineered URIs they put to much effort in to give the URI some kind of logical sense when actually neither client nor server will interpret it anyway as they will probably use the link relation name given for the URI.

GraphQL on the other hand is a query language which gives the client the power to request specific fields and elements it wants to retrieve from the server. It is, loosely speaking, some kind of SQL for the Web. It therefore has to have knowlege on the available data beforehand which couples clients somehow to the server. If the server will rename some of the fields, the client might not be able to retrieve that kind of information further, though I'm not a GraphQL expert.

As stated above, REST is often confused for a JSON based HTTP API that allows to perform queries on directly mapped DB entries/entities. Keep in mind that REST doesn't prohibit this, though its focus is on the decoupling of peers not the retrieval aspect of some Web exposed database entries.

Answer 2

In the context of Azure AD and its APIs, the term REST API is used when you access the Microsoft Graph service directly. You write all the http communication code, authentication, JSON parsing etc.

The term Graph API or Graph client is a reference to the Microsoft-developed Graph Client SDK which encapsulates the above.

If there is no SDK for your platform, you need to use the REST API directly. Otherwise, I would recommend to use the SDK.