Introduction

There is no single global "maximum number of concurrent HttpWebRequest calls" in .NET. The practical limit depends on connection settings, the target host, the runtime, and the server you are talking to.

The important limit is usually per host

With HttpWebRequest, the classic bottleneck is not the number of request objects you create. It is the number of simultaneous connections allowed to the same endpoint.

In .NET Framework, this is commonly controlled through ServicePointManager.DefaultConnectionLimit and per-host service points.

A typical tuning example looks like this:

1using System;
2using System.Net;
3
4class Program
5{
6    static void Main()
7    {
8        ServicePointManager.DefaultConnectionLimit = 20;
9        Console.WriteLine(ServicePointManager.DefaultConnectionLimit);
10    }
11}

If you leave the default low and fire many requests to the same server, extra requests queue rather than execute truly in parallel.

Why people see the number 2 so often

Historically, desktop .NET Framework applications often defaulted to a very low per-host connection limit, commonly 2 for HTTP 1.1 style usage. That is why old examples talk about only two concurrent requests.

That does not mean your program can only create two HttpWebRequest objects. It means only a small number of active connections to one host may proceed at once unless you change the setting.

ASP.NET-hosted applications and newer runtimes may behave differently, which is another reason there is no universal one-number answer.

Concurrency is more than the client setting

Even if you increase the connection limit, real throughput still depends on:

• server-side connection limits
• load balancers and proxies
• DNS and socket exhaustion
• request latency
• thread usage in synchronous code

If your code issues synchronous requests, blocked threads may become the bottleneck long before the network stack does.

A practical example

This example creates several requests, but how many run in parallel to one server depends on the connection limit and server behavior.

1using System;
2using System.IO;
3using System.Net;
4using System.Threading.Tasks;
5
6class Program
7{
8    static async Task Main()
9    {
10        ServicePointManager.DefaultConnectionLimit = 10;
11
12        Task[] tasks = new Task[5];
13        for (int i = 0; i < tasks.Length; i++)
14        {
15            tasks[i] = Task.Run(() =>
16            {
17                var request = (HttpWebRequest)WebRequest.Create("https://example.com");
18                using var response = (HttpWebResponse)request.GetResponse();
19                using var reader = new StreamReader(response.GetResponseStream());
20                Console.WriteLine(reader.ReadLine());
21            });
22        }
23
24        await Task.WhenAll(tasks);
25    }
26}

Modern guidance

HttpWebRequest is legacy API surface in modern .NET. For new code, HttpClient is generally preferred because it has better connection management, async support, and clearer lifetime rules.

So if the deeper question is really about high-concurrency HTTP clients, the better engineering move is often to migrate rather than to keep tuning HttpWebRequest.

Common Pitfalls

The biggest mistake is confusing request objects with active network connections. Creating many HttpWebRequest instances does not guarantee many concurrent in-flight requests.

Another issue is increasing DefaultConnectionLimit without measuring the server's behavior. A client-side increase does not force the server to handle more work well.

It is also easy to forget that synchronous GetResponse() calls tie up worker threads. Under load, thread starvation can look like a networking limit.

Finally, if you are on a newer .NET stack, spending too much effort on HttpWebRequest may be the wrong optimization target. HttpClient is the better default for modern applications.

Summary

• There is no single hard maximum for concurrent HttpWebRequest usage.
• The practical limit is often the per-host connection limit, not the number of request objects.
• In classic .NET Framework, the default per-host limit was often very low.
• 'ServicePointManager.DefaultConnectionLimit can raise that limit for old-style code.'
• For modern high-concurrency HTTP work, prefer HttpClient over HttpWebRequest.