REST API vs SOAP API

Updated on: September 1, 2025

REST API vs SOAP API vs GraphQL API vs WebSocket API – Types of API explained.

What Are APIs?

Application Programming Interfaces, or APIs, facilitate communication and feature or data sharing between various software systems.

They are necessary for effectively linking services and apps.

This guide uses C# examples to compare types of API like REST and SOAP APIs, as well as GraphQL API and WebSocket APIs.

1) Representational State Transfer, or REST API

What is it?

A well-liked HTTP web communication architecture.
It functions nicely with CRUD operations and is stateless.

When to apply it:

For straightforward, scalable HTTP APIs.
Ideal for microservices and CRUD-based applications.

An example in C# that uses a REST API in.NET Core:

using System.Net.Http;
using System.Threading.Tasks;

class Program
{
    static async Task Main()
    {
        using var client = new HttpClient();
        var response = await client.GetAsync("https://api.example.com/data");
        var content = await response.Content.ReadAsStringAsync();
        Console.WriteLine(content);
    }
}

2) Simple Object Access Protocol, or SOAP API

What is it?

A common corporate application protocol for transmitting structured XML-based data.

When to apply it:

For strong security and stringent standards.
Perfect for enterprise apps, payment gateways, and financial systems.

C# Example (Using.NET Core to Call the SOAP API):

using System;
using System.ServiceModel;

[ServiceContract]
public interface IMyService
{
    [OperationContract]
    string MyFunction(string input);
}

class Program
{
    static void Main()
    {
        var binding = new BasicHttpBinding();
        var endpoint = new EndpointAddress("https://example.com/service.svc");
        var channelFactory = new ChannelFactory<IMyService>(binding, endpoint);
        var client = channelFactory.CreateChannel();

        var result = client.MyFunction("Hello");
        Console.WriteLine(result);
    }
}

3) The GraphQL API

What is it?

A versatile API query language.
Without over-fetching, it enables clients to retrieve precisely the data they require.

When to apply it:

For intricate interactions between data.
to refrain from retrieving superfluous fields.

An example of using C# to query GraphQL in.NET Core:

using System;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;

class Program
{
    static async Task Main()
    {
        var query = "{ posts { id title author { name } } }";
        var jsonContent = new StringContent(
            "{\"query\":\"" + query.Replace("\"", "\\\"") + "\"}",
            Encoding.UTF8,
            "application/json"
        );

        using var client = new HttpClient();
        var response = await client.PostAsync("https://example.com/graphql", jsonContent);
        var content = await response.Content.ReadAsStringAsync();
        Console.WriteLine(content);
    }
}

4) WebSocket API

What is it?

A protocol that allows a client and server to communicate in both directions over time.

When to apply it:

For real-time communication, such as chat applications.
for applications that require constant data flow.

An example in C# that uses WebSocket in.NET Core:

using System;
using System.Net.WebSockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

class Program
{
    static async Task Main()
    {
        using var socket = new ClientWebSocket();
        await socket.ConnectAsync(new Uri("wss://example.com/socket"), CancellationToken.None);

        var message = Encoding.UTF8.GetBytes("Hello Server");
        await socket.SendAsync(message, WebSocketMessageType.Text, true, CancellationToken.None);

        var buffer = new byte[1024];
        var result = await socket.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);
        Console.WriteLine("Message from server: " + Encoding.UTF8.GetString(buffer, 0, result.Count));
    }
}

REST vs SOAP vs GraphQL — Which One to Choose?

RESTful API:
Ideal for the majority of web services. Widely supported, easy to use, and scalable.

SOAP API:
Ideal for enterprise systems that adhere to standards and are safe. Strong reliability but more setup.

GraphQL API:
Best for apps with complex or evolving data needs. Get precisely what you require.