SignalR vs gRPC on ASP.NET Core - which one to choose - Scientific Programmer (2023)

My book, SignalR on .NET 6 – the complete guide, is out now! Also available in print.

A while ago, when ASP.NET Core didn’t even exist, Microsoft has created a library for .NET Framework-based ASP.NET that enabled a two-way communication between the clients and a server in real time. This library was called SignalR.

The goal of this library was to significantly simplify the implementation of standard communication protocols that were normally used for this type of communication. These protocols included WebSocket, long polling and server-sent events.

Any of these protocols could be used directly, but none of them was very easy to use on its own. SingnalR made it easy by hiding away all complex implementation details.

With the introduction of ASP.NET Core version 2.1, this library was completely re-written and became a standard part of ASP.NET Core.

gRPC is a communication protocol that was originally developed by Google. Unlike SignalR, it doesn’t leverage the usage of existing protocols. It’s a completely self-contained protocol that leverages new features of HTTP/2, which was made generally available in 2015.

gRPC implementations are available in most of the major programming languages. And, since ASP.NET Core 3.0 has been released, it became an integral part of ASP.NET Core, just like SignalR did before it.

Both of these technologies are extremely useful and they can be used for similar purposes. Whether one is better than the other depends purely on the context.

Today, we will have a look at the pros and cons of each of these technologies in different contexts so you can be better equipped to decide which one to use.

Where SignalR beats gRPC

I have previously outlined the key benefits of using SignalR compared to writing equivalent functionality manually. These can be summarized as follows:

  • All complexity is abstracted away
  • No more need for AJAX
  • Works with any types of client (even pure WebSocket ones)
  • Can be scaled out very easily
  • Used in various parts of ASP.NET out of the box (e.g. in Blazor Server)

The most fundamental benefit of using SignalR is how it abstracts away complex implementations of WebSocket, long polling and server-sent events. For example, while a pure WebSocket implementation may look like this:

SignalR vs gRPC on ASP.NET Core - which one to choose - Scientific Programmer (1)

The SignalR equivalent will look like this:

SignalR vs gRPC on ASP.NET Core - which one to choose - Scientific Programmer (2)

However, this time, we are not comparing SignalR against writing your own implementations manually. We are comparing it specifically against gRPC. So, here are some of the advantages that SignalR has over gRPC:

1. No need to use HTTP/2 (i.e. it works virtually anywhere)

Without HTTP/2, you cannot have gRPC. This means that not all systems can use it. If either the client or the server application you are working on is hosted on a system that doesn’t have HTTP/2 support, there is nothing you can do to make it work.

SignalR, on the other hand, works with basic HTTP. This is why it can be used on almost any system.

Of course, not all systems can use WebSocket protocol. So you may not be able to use SignalR in the most efficient way in some setups. But this is precisely why it has two fallback protocols – server-sent events and long polling.

And the fact that SignalR is not using HTTP/2 doesn’t mean that it is less performant than gRPC. Yes, HTTP/2 provides many performance benefits, such as compressed headers, which increase the performance. And the messaging mechanism used by gRPC, protocol buffer, serializes messages in an efficient way, making the payload as small as possible, which increases the performance even further.

However, SignalR, when used with WebSocket, is comparable in its efficiency. First of all, it only uses HTTP header to establish the initial connection, so the header compression provided by HTTP/2 is almost irrelevant. Secondly, it can be configured to use a proprietary binary JSON protocol called MessagePack, which, just like protocol buffer, substantially reduces the payload size and therefore improves the performance.

Performance-wise, SignalR and gRPC are comparable. And both of them beat the standard HTTP-based communication hands down.

2. Events can be initiated by either a client or the server

One limitation of gRPC is that it’s still largely similar to a standard request-response model employed by HTTP. Only the client can initiate events. The server can only respond to those.

There is a work-around. gRPC can use server streaming, where the client sends the initial request and then both the client and the server keep the stream open, so the server can put messages into it when specific action is triggered.

But the implementation of this would have to be fairly clumsy. Streaming calls are not designed to be used like this. You would need to add loops to both the client and the server and you will need to manage the connection status manually. Plus you would need to do it for every individual method that needs to communicate both ways.

With SignalR, on the other hand, all you have to do from the client is send the initial connection request. After this, both the client and the server can send messages to each other by using any of each other’s endpoints. All you have to do is add methods on the server side and add named event listeners on the client side. The connection can remain open indefinitely. SignalR library itself will manage the connection status for you by sending heartbeats at regular intervals and by attempting to reconnect automatically if the connection is broken.

And, just like gRPC, SignalR is fully capable of streaming real time data both to and from the server.

3. No need to write any communication contracts and generate code from them

To enable gRPC communication, you will need to write a proto file that would contain definitions of the gRPC services and all the remote procedures on these services that clients will be able to call. Once this is done, you will need to run a language-specific tool to generate code that would correspond with these definitions. And only then you can start writing the actual logic.

With SignalR, you don’t have to do any of this. All you need to do is write any arbitrary method definitions in your server-side app and write named message handlers on your client.

Of course, this doesn’t come without its own potential issues. For example, you need to be extra careful that the method names are spelled the same on both the client and the server. But nevertheless, not having to write an explicitly defined contract and not having to rely on various tools to generate a code based on this contract substantially speeds up the development process.

Where gRPC beats SignalR

Even though SignalR has its advantages over gRPC, the latter would be a better solution in certain situations. Here is the areas where gRPC has an edge over SignalR.

1. Much easier API versioning

Even though, when you are using gRPC, you have to write an explicit contract between the client and the server, it’s not always a disadvantage. For example, the way proto format has been designed allows you to easily apply API versioning.

When defining a structure of messages in a proto file, you will be required to give each of your fields a unique integer number. This would look like this:

SignalR vs gRPC on ASP.NET Core - which one to choose - Scientific Programmer (3)

And this mechanism is what makes API versioning easy. Let’s imagine a scenario which will help us to see why is it so.

In the first version of your gRPC service, you have a message definition that contains two fields as per the above screenshot – request_id and payload_collection. These fields have been assigned numbers 1 and 2 respectively. Now, for our second version, we have decided to add a new field, timestamp, and assign number 3 to it.

As long as we haven’t modified any of the fields with the existing numbers, the clients that haven’t received this update will still work with the new message definition. If this is a definition of a response object that server sends back to the client, the client will simply ignore the new field, as a field with number 3 is not outlined in its own proto definition. If this was a request object, then the client would populate the first two fields and the field with number 3 would be given a default value on the server-side.

In either case, both the client and the server will still work. The key is not to modify the fields with the existing numbers. Otherwise things may break.

SignalR doesn’t have any of this. Of course, there is nothing that stops you from implementing your own API versioning mechanism that is similar to this. But with gRPC, you already have such a mechanism in place, so you won’t have to re-invent the wheel.

2. Libraries available in pretty much any language

Even though SignalR is open source, it is still Microsoft’s proprietary technology. And this is why SignalR server can only be written in Microsoft’s own back-end languages (primarily C#, although using F# is also supported).

SignalR clients can also be written only in a limited number of languages. At the time of writing, only .NET, JavaScript and Java clients were supported. Of course, you can write your own client in any language by using pure WebSocket, but you will loose all the benefits of using SignalR if you’ll choose to do it this way.

gRPC, on the other hand, is an open standard. And this is why it is available on many popular languages. This applies to both the client and the server.

3. Easier to apply in microservice architecture

Another area where gRPC beats SignalR hands-down is communication between microservices and containers.

More and more organizations are getting rid of large monolithic apps by splitting them up into smaller components that can be executed and updated individually. However, these components still form a large distributed application. And this is why there needs to be an efficient mechanism in place for them to communicate with each other.

Various forms of remote procedure call (RPC) mechanisms were traditionally used for this purpose. They tend to be more efficient than HTTP, as they don’t have as much data in the headers. Also, they don’t have to adhere to outdated common standards and can be completely proprietary. Azure Service Fabric Remoting mechanism is an example of this.

gRPC eliminated the need to use proprietary RPC mechanisms for different types of technologies. It’s an open standard, so any system can use it. And it’s highly efficient, because it’s running on top of HTTP/2.

SignalR, on the other hand, wouldn’t be efficient enough to get microservices to communicate with each other. Even though it allows you to write code that looks like the client and the server are calling each other’s methods remotely, this is not what happens under the hood. Instead, a persistent connection is established between the client and the server. And the connection is maintained by sending small heartbeat messages both ways.

If you have a distributed application with a large number of moving parts, imagine how much bandwidth would be used if all individual components opened a number of persistent connections to communicate with each other. With gRPC, on the other hand, any data is exchanged only when such exchange is needed. The only time you would need any long-lasting connection is when you use streams. But even then you would close the stream once you transfer all the data through.


Both SignalR and gRPC are great communication mechanisms that every Microsoft-stack software developer should learn. And neither is better than the other. There are just specific scenarios that favor the usage of a particular one.

For example, if you need to build something where the server regularly communicates with the client, SignalR would be better. If, on the other hand, you are building a large distributed application with many moving parts, gRPC would be a better mechanism for those parts to communicate with one another.

P.S. if you want to learn more about SignalR, you can check out my book SignalR on .NET 6 – the complete guide.


What is better than SignalR? ›

There are many alternatives for signalR that are used, like Firebase, pusher, webRTC, RabbitMQ, gRPC, and MQTT.

Which activity is SignalR primarily used for? ›

SignalR can be used to add any sort of "real-time" web functionality to your ASP.NET application. While chat is often used as an example, you can do a whole lot more. Any time a user refreshes a web page to see new data, or the page implements long polling to retrieve new data, it is a candidate for using SignalR.

How can I improve my SignalR performance? ›

Reducing message size

Names can be shortened in messages from the client to the server as well, using the same method. Reducing the memory footprint (that is, the amount of memory used for the message) of the message object can also improve performance.

Is SignalR obsolete? ›

This browser is no longer supported. Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support.

What is the difference between SignalR and gRPC? ›

gRPC is a communication protocol that was originally developed by Google. Unlike SignalR, it doesn't leverage the usage of existing protocols. It's a completely self-contained protocol that leverages new features of HTTP/2, which was made generally available in 2015.

What are the limitations of SignalR? ›

SignalR uses per-connection buffers to manage incoming and outgoing messages. By default, SignalR limits these buffers to 32 KB. The largest message a client or server can send is 32 KB. The maximum memory consumed by a connection for messages is 32 KB.

How many users can SignalR handle? ›

In the default mode, the app server creates five server connections with Azure SignalR Service. The app server uses the Azure SignalR Service SDK by default. In the following performance test results, server connections are increased to 15 (or more for broadcasting and sending a message to a big group).

Why should I use SignalR? ›

SignalR provides features such as automatic reconnections, fallback transports, or the ability to broadcast messages to all connected clients, or only to specific groups of clients.

Does SignalR keep connection alive? ›

If the transport connection fails or the server fails, the SignalR connection doesn't go away immediately because the client still has the information it needs to automatically re-establish a new transport connection to the same SignalR URL.

Does SignalR use JSON? ›

ASP.NET Core SignalR supports two protocols for encoding messages: JSON and MessagePack.

What are the most common process managers for asp net core app that uses Kestrel server for reverse proxy? ›

The most common process managers for ASP.NET Core are:
  • Linux. Nginx. Apache.
  • Windows. IIS. Windows Service.
Nov 16, 2022

Is SignalR faster than rest? ›

In most cases, REST is faster. And the SignalR is faster than the REST. Situation changes when you start making parallel calls. More parallel calls there are - gRPC-Web is faster.

How will you improve performance of ASP NET core application? ›

In this article
  1. Cache aggressively.
  2. Understand hot code paths.
  3. Avoid blocking calls.
  4. Return large collections across multiple smaller pages.
  5. Minimize large object allocations.
  6. Optimize data access and I/O.
  7. Pool HTTP connections with HttpClientFactory.
  8. Keep common code paths fast.
Dec 21, 2022

What is difference between SignalR and WebSocket? ›

WebSockets is actually the underlying transport that SignalR uses, at least most of the time. SignalR has the ability to fall back to other ways of transporting messages, such as long-polling over HTTP. This is useful in situations where you don't have WebSockets support.

Is ASP NET core still relevant? ›

It is still widely used by developers and remains a top open-source framework on GitHub. In fact, according to the Stack Overflow 2021 developer survey, more than 15% of developers still prefer ASP.NET over other frameworks for their web development needs.

How secure is SignalR? ›

SignalR uses encryption and a digital signature to protect the connection token. For each request, the server validates the contents of the token to ensure that the request is coming from the specified user.

Is ASP.NET still relevant 2022? ›

ASP.NET is one of the most widely used frameworks among developers due to its enormous advantages. It is now ranked in the top 10 web frameworks as of 2022.

What are the disadvantages of gRPC? ›

Limited browser support. It's impossible to directly call a gRPC service from a browser today. gRPC heavily uses HTTP/2 features and no browser provides the level of control required over web requests to support a gRPC client.

Why gRPC is not widely used? ›

As CircleCI reports, gRPC can also be fragile and more complex than the alternatives. Thus, it's not always the best solution for every problem in which the need for high-speed communication over a network is a critical factor.

When should I use gRPC? ›

Basically, gRPC is another alternative that could be useful in certain circumstances: large-scale microservices connections, real-time communication, low-power, low-bandwidth systems, and multi-language environments. Unlike REST, gRPC makes the most out of HTTP/2, with multiplexed streaming and binary protocol framing.

Does SignalR use WebSockets? ›

ASP.NET Core SignalR is a library that simplifies adding real-time web functionality to apps. It uses WebSockets whenever possible. For most applications, we recommend SignalR rather than raw WebSockets.

How to use SignalR in asp net core? ›

In this article
  1. Prerequisites.
  2. Create a web app project.
  3. Add the SignalR client library.
  4. Create a SignalR hub.
  5. Configure SignalR.
  6. Add SignalR client code.
  7. Run the app.
  8. Publish to Azure.
5 days ago

How many connection limits does SignalR Chrome have? ›

And it would be right, as for chrome the limit is 6 simultaneous connections to a single domain. Limitation in number of requests per domain results from HTTP 1.1 specification – it says that there are maximum two requests, however in real life there are more of them – it depends on a browser.

Is SignalR full duplex? ›

SignalR supports full duplex communication that allows the client and server to transfer data back and forth.

How old is SignalR? ›

Original author(s)David Fowler and Damian Edwards
Initial release18 February 2013
Stable release2.4.3 / January 14, 2022
8 more rows

What is the maximum message size in Azure SignalR? ›

There is no limit to server message size, but under 16MB is recommended. App server can set a limit for client message size. Default is 32KB. For more information, see Security considerations in ASP.NET Core SignalR.

What is the difference between SignalR and Ajax? ›

SignalR uses WebSockets but ajax uses HttpRequest. In AJAX the client (browser) sends a request to the server and then receives a reply. When using SignalR, the Server can initiate contact with the client, the browser would receive the update when and only if there is something new to show the user.

Does AWS support SignalR? ›

Azure SignalR Service doesn't have in-built support for other serverless platforms, such as AWS Lambda or Google Cloud Functions.

What is ASP.NET SignalR vs asp net Core SignalR? ›

The scaleout model for ASP.NET SignalR allows clients to reconnect and send messages to any server in the farm. In ASP.NET Core SignalR, the client must interact with the same server for the duration of the connection. For scaleout using Redis, that means sticky sessions are required.

Does SignalR require sticky sessions? ›

SignalR requires that all HTTP requests for a specific connection be handled by the same server process. When SignalR is running on a server farm (multiple servers), "sticky sessions" must be used. "Sticky sessions" are also called session affinity by some load balancers.

What is the difference between persistent connection and hub in SignalR? ›

With persistent connections you have to embed the message type in the payload (see Raw sample) but hubs gives you the ability to do RPC over a connection (lets you call methods on on the client from the server and from the server to the client). Another big thing is model binding.

What platform does SignalR client supports? ›

The . NET client runs on any platform supported by ASP.NET Core. For example, Xamarin developers can use SignalR for building Android apps using Xamarin. Android 8.4.

Which programming language is JSON best used? ›

Languages such as PHP, Python, C#, C++, and Java provide very good support for the JSON data interchange format. All of the popular programming languages that support service-oriented architectures understand the importance of JSON and its implementation for data transfer, and thus have provided great support for JSON.

Do people still use JSON? ›

JSON, or JavaScript Object Notation, is a format used to represent data. It was introduced in the early 2000s as part of JavaScript and gradually expanded to become the most common medium for describing and exchanging text-based data. Today, JSON is the universal standard of data exchange.

What is the difference between invoke and send in SignalR? ›

Unlike the invoke method, the send method doesn't wait for a response from the server. The send method returns a JavaScript Promise . The Promise is resolved when the message has been sent to the server. If there is an error sending the message, the Promise is rejected with the error message.

Which database is best for ASP.NET Core? ›

  • SQLite.
  • Postgres.
  • MySQL.
Aug 13, 2022

What is Kestrel and what are advantages of Kestrel in ASP.NET Core? ›

Kestrel is the web server that's included by default in ASP.NET Core project templates. Kestrel supports the following scenarios: HTTPS. Opaque upgrade used to enable WebSockets. Unix sockets for high performance behind Nginx.

Is Kestrel production ready? ›

Yes, Kestrel is production ready and is supported on all platforms and versions that . NET Core supports, but if your application is available on public networks Microsoft recommend that you use it with a reverse proxy: Even if a reverse proxy server isn't required, using a reverse proxy server might be a good choice.

What is the equivalent of SignalR in node? ›

Top Alternatives to SignalR
  • Firebase. Firebase is a cloud service designed to power real-time, collaborative applications. ...
  • Pusher. Pusher is the category leader in delightful APIs for app developers building communication and collaboration features. ...
  • RabbitMQ. ...
  • WebRTC. ...
  • MQTT. ...
  • gRPC. ...
  • WCF. ...
  • Kafka.

Which ASP.NET is better? ›

Which is faster, ASP.NET or PHP? ASP.NET performs comparatively faster than PHP; because compiled languages are usually faster than interpreted languages.

How many SignalR connections can a server handle? ›

IIS on client operating systems has a limit of 10 concurrent connections. SignalR's connections are: Transient and frequently re-established. Not disposed immediately when no longer used.

What are the advantages of using SignalR? ›

Azure SignalR Service simplifies the process of adding real-time web functionality to applications over HTTP. This real-time functionality allows the service to push content updates to connected clients, such as a single page web or mobile application.

What will replace WebSockets? ›

WebTransport is a new specification that could offer an alternative to WebSockets. For applications that need low-latency, event-driven communication between endpoints, WebSockets has been the go-to choice, but WebTransport may change that.

Which language is best for WebSockets? ›

A WebSocket server can be written in any server-side programming language that is capable of Berkeley sockets, such as C(++), Python, PHP, or server-side JavaScript.

What is the data size limit for SignalR? ›

SignalR uses per-connection buffers to manage incoming and outgoing messages. By default, SignalR limits these buffers to 32 KB. The largest message a client or server can send is 32 KB. The maximum memory consumed by a connection for messages is 32 KB.

Is ASP.NET Core in demand? ›

The demand for . Net developers is increasing worldwide because it is one of the most popular programming languages and has a lot of uses. In the future, the need for . Net developers will also increase because more businesses will use this technology in their products and services.

What is the best ASP.NET Core course? ›

7 Best Online Courses to learn ASP . NET in 2023
  • The Complete ASP.NET MVC 5 Course. ...
  • Build an app with ASPNET Core and Angular from scratch. ...
  • Complete guide to building an app with . ...
  • ASP.NET Core Fundamentals By Scott Allen [Pluralsight Course] ...
  • Build a Real-world App with ASP.NET Core and Angular 2 (4+)


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