WebSocket vs gRPC - When to Use Which

WebSocket vs gRPC represents one of the most common architectural decisions when building real-time communication systems. Both protocols enable bidirectional streaming and persistent connections, but they serve different use cases and come with distinct trade-offs. Understanding when to use WebSocket and when to choose gRPC streaming can significantly impact your application’s performance, maintainability, and scalability.

This guide provides a technical comparison of WebSocket and gRPC, examining their underlying mechanisms, performance characteristics, browser support, and practical use cases. Whether you’re building a chat application, real-time dashboard, or microservices architecture, this analysis will help you make an informed decision.

Quick Comparison: WebSocket vs gRPC

Feature	WebSocket	gRPC
Protocol	WebSocket (RFC 6455) over TCP	HTTP/2 with Protocol Buffers
Transport	Full-duplex TCP connection	HTTP/2 streams with multiplexing
Message Format	Text or binary (flexible)	Protocol Buffers (binary)
Browser Support	Native support in all browsers	Requires gRPC-Web proxy
Streaming Types	Bidirectional only	Unary, server, client, bidirectional
Performance	Low overhead, minimal framing	Efficient binary serialization, HTTP/2 benefits
Schema	No enforced schema	Strongly typed with .proto files
Use Case	Real-time web apps, gaming, chat	Microservices, polyglot systems, APIs
Load Balancing	Requires session affinity	HTTP/2-aware load balancing needed
Compression	Optional (permessage-deflate)	Built-in with HTTP/2 header compression

How WebSocket Works

WebSocket establishes a persistent, full-duplex connection between client and server through an HTTP upgrade handshake. Once the connection is established, both parties can send messages independently without the request-response overhead of traditional HTTP.

WebSocket Connection Flow:

// Client-side WebSocket implementation
const ws = new WebSocket('wss://api.example.com/realtime');

ws.onopen = () => {
  console.log('WebSocket connection established');

  // Send messages anytime
  ws.send(JSON.stringify({
    type: 'subscribe',
    channel: 'stock-prices',
    symbols: ['AAPL', 'GOOGL']
  }));
};

ws.onmessage = (event) => {
  const data = JSON.parse(event.data);
  console.log('Received:', data);

  // Handle real-time updates
  if (data.type === 'price-update') {
    updateStockPrice(data.symbol, data.price);
  }
};

ws.onerror = (error) => {
  console.error('WebSocket error:', error);
};

ws.onclose = (event) => {
  console.log('Connection closed:', event.code, event.reason);
};

Server-side WebSocket (Node.js):

const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });

wss.on('connection', (ws) => {
  console.log('Client connected');

  ws.on('message', (message) => {
    const data = JSON.parse(message);

    if (data.type === 'subscribe') {
      // Subscribe client to updates
      data.symbols.forEach(symbol => {
        subscribeToSymbol(symbol, ws);
      });
    }
  });

  ws.on('close', () => {
    console.log('Client disconnected');
  });
});

// Broadcast price updates to subscribed clients
function broadcastPriceUpdate(symbol, price) {
  const message = JSON.stringify({
    type: 'price-update',
    symbol,
    price,
    timestamp: Date.now()
  });

  wss.clients.forEach((client) => {
    if (client.readyState === WebSocket.OPEN) {
      client.send(message);
    }
  });
}

WebSocket operates at the application layer with minimal protocol overhead. After the initial handshake, frames contain only 2-14 bytes of metadata per message, making it extremely efficient for high-frequency messaging.

For a deeper dive into WebSocket fundamentals, see What is WebSocket.

How gRPC Streaming Works

gRPC uses HTTP/2 as its transport protocol and Protocol Buffers for serialization. Unlike WebSocket’s single bidirectional streaming mode, gRPC offers four distinct RPC types: unary (request-response), server streaming, client streaming, and bidirectional streaming.

gRPC Service Definition (.proto file):

syntax = "proto3";

package stocks;

service StockService {
  // Server streaming: client sends one request, receives stream of responses
  rpc StreamPrices(SubscribeRequest) returns (stream PriceUpdate) {}

  // Bidirectional streaming: both sides send streams
  rpc BidirectionalTrade(stream TradeOrder) returns (stream TradeConfirmation) {}
}

message SubscribeRequest {
  repeated string symbols = 1;
}

message PriceUpdate {
  string symbol = 1;
  double price = 2;
  int64 timestamp = 3;
}

message TradeOrder {
  string symbol = 1;
  int32 quantity = 2;
  double limit_price = 3;
}

message TradeConfirmation {
  string order_id = 1;
  string status = 2;
}

gRPC Client Implementation (Go):

package main

import (
    "context"
    "io"
    "log"

    pb "example.com/stocks"
    "google.golang.org/grpc"
)

func main() {
    conn, err := grpc.Dial("localhost:50051", grpc.WithInsecure())
    if err != nil {
        log.Fatalf("Failed to connect: %v", err)
    }
    defer conn.Close()

    client := pb.NewStockServiceClient(conn)

    // Server streaming
    stream, err := client.StreamPrices(context.Background(), &pb.SubscribeRequest{
        Symbols: []string{"AAPL", "GOOGL"},
    })
    if err != nil {
        log.Fatalf("Error calling StreamPrices: %v", err)
    }

    // Receive streamed price updates
    for {
        update, err := stream.Recv()
        if err == io.EOF {
            break
        }
        if err != nil {
            log.Fatalf("Error receiving update: %v", err)
        }

        log.Printf("Price update: %s = $%.2f (ts: %d)",
            update.Symbol, update.Price, update.Timestamp)
    }
}

gRPC Server Implementation (Go):

package main

import (
    "log"
    "net"
    "time"

    pb "example.com/stocks"
    "google.golang.org/grpc"
)

type stockServer struct {
    pb.UnimplementedStockServiceServer
}

func (s *stockServer) StreamPrices(req *pb.SubscribeRequest, stream pb.StockService_StreamPricesServer) error {
    ticker := time.NewTicker(1 * time.Second)
    defer ticker.Stop()

    for {
        select {
        case <-ticker.C:
            for _, symbol := range req.Symbols {
                price := getCurrentPrice(symbol) // Your price fetching logic

                if err := stream.Send(&pb.PriceUpdate{
                    Symbol:    symbol,
                    Price:     price,
                    Timestamp: time.Now().Unix(),
                }); err != nil {
                    return err
                }
            }
        case <-stream.Context().Done():
            return stream.Context().Err()
        }
    }
}

func main() {
    listener, err := net.Listen("tcp", ":50051")
    if err != nil {
        log.Fatalf("Failed to listen: %v", err)
    }

    grpcServer := grpc.NewServer()
    pb.RegisterStockServiceServer(grpcServer, &stockServer{})

    log.Printf("gRPC server listening on :50051")
    if err := grpcServer.Serve(listener); err != nil {
        log.Fatalf("Failed to serve: %v", err)
    }
}

gRPC streaming leverages HTTP/2’s multiplexing capability, allowing multiple streams over a single TCP connection. This enables efficient use of network resources and automatic flow control.

Browser Support Differences

Browser support is a critical factor when choosing between WebSocket and gRPC for client-facing applications.

WebSocket Browser Support

WebSocket has native browser support across all modern browsers and has been available since 2011. No additional libraries, proxies, or workarounds are required:

// Native WebSocket API works in all browsers
const ws = new WebSocket('wss://api.example.com');

gRPC Browser Limitations

gRPC requires HTTP/2 and trailers, which browsers don’t fully expose to JavaScript. This necessitates gRPC-Web, a JavaScript implementation that uses a proxy to translate between gRPC and browser-compatible HTTP/1.1 or HTTP/2.

gRPC-Web Architecture:

Browser (gRPC-Web client)
    ↓ HTTP/1.1 or HTTP/2
gRPC-Web Proxy (Envoy, Nginx)
    ↓ gRPC over HTTP/2
Backend gRPC Service

gRPC-Web Client Example:

const {StockServiceClient} = require('./stocks_grpc_web_pb.js');
const {SubscribeRequest} = require('./stocks_pb.js');

const client = new StockServiceClient('http://localhost:8080');

const request = new SubscribeRequest();
request.setSymbolsList(['AAPL', 'GOOGL']);

const stream = client.streamPrices(request, {});

stream.on('data', (response) => {
  console.log('Price update:', response.getSymbol(), response.getPrice());
});

stream.on('error', (err) => {
  console.error('Stream error:', err);
});

stream.on('end', () => {
  console.log('Stream ended');
});

The gRPC-Web proxy requirement adds deployment complexity and latency compared to WebSocket’s direct connection. For browser-based applications, WebSocket offers a simpler, more performant solution.

Performance Comparison

Performance characteristics differ significantly between WebSocket and gRPC depending on your specific use case.

Message Size and Serialization

Protocol Buffers (gRPC) provide highly efficient binary serialization:

message PriceUpdate {
  string symbol = 1;      // Variable length
  double price = 2;       // 8 bytes
  int64 timestamp = 3;    // Variable length (optimized)
}

A typical price update might serialize to 20-30 bytes with Protocol Buffers.

WebSocket with JSON (common pattern):

{
  "symbol": "AAPL",
  "price": 178.42,
  "timestamp": 1707840000000
}

The same data in JSON requires 60-70 bytes. However, WebSocket also supports binary formats:

// WebSocket with Protocol Buffers
const priceUpdate = PriceUpdate.encode({
  symbol: 'AAPL',
  price: 178.42,
  timestamp: Date.now()
}).finish();

ws.send(priceUpdate);

Using Protocol Buffers over WebSocket combines the efficiency of binary serialization with WebSocket’s low overhead.

Throughput and Latency

WebSocket advantages:

• Minimal frame overhead (2-14 bytes per message)
• No HTTP/2 stream management overhead
• Direct TCP connection without intermediate layers
• Lower latency for simple messaging patterns

gRPC advantages:

• HTTP/2 multiplexing eliminates head-of-line blocking at application layer
• Automatic flow control and congestion management
• Efficient header compression (HPACK)
• Better performance for many concurrent streams

Benchmark comparison (approximate, varies by implementation):

Test: 100,000 small messages (50 bytes payload)

WebSocket:
- Throughput: ~200,000 msg/sec
- Average latency: 0.5ms
- Connection overhead: ~150ms (initial handshake)

gRPC Streaming:
- Throughput: ~150,000 msg/sec
- Average latency: 0.8ms
- Connection overhead: ~100ms (HTTP/2 connection)

For high-frequency, low-latency messaging (gaming, financial trading), WebSocket typically performs better. For microservices with many concurrent streams, gRPC’s HTTP/2 foundation provides advantages.

GraphQL Subscriptions Over WebSocket

GraphQL subscriptions commonly use WebSocket as the transport layer, combining GraphQL’s query flexibility with WebSocket’s real-time capabilities.

GraphQL subscription example:

import { ApolloClient, InMemoryCache, split } from '@apollo/client';
import { GraphQLWsLink } from '@apollo/client/link/subscriptions';
import { createClient } from 'graphql-ws';
import { getMainDefinition } from '@apollo/client/utilities';

// WebSocket link for subscriptions
const wsLink = new GraphQLWsLink(createClient({
  url: 'wss://api.example.com/graphql',
}));

// Subscribe to real-time updates
const subscription = gql`
  subscription OnPriceUpdate($symbols: [String!]!) {
    priceUpdates(symbols: $symbols) {
      symbol
      price
      timestamp
    }
  }
`;

client.subscribe({
  query: subscription,
  variables: { symbols: ['AAPL', 'GOOGL'] }
}).subscribe({
  next: ({ data }) => {
    console.log('Price update:', data.priceUpdates);
  }
});

GraphQL subscriptions over WebSocket provide a good middle ground: you get WebSocket’s native browser support and performance with GraphQL’s flexible querying. However, gRPC’s strongly typed schemas and code generation offer better type safety for non-browser environments.

REST vs WebSocket

While comparing WebSocket vs gRPC, it’s worth noting how both differ from traditional REST APIs.

REST API limitations for real-time data:

// Polling approach with REST
async function pollPrices() {
  setInterval(async () => {
    const response = await fetch('https://api.example.com/prices?symbols=AAPL,GOOGL');
    const data = await response.json();
    updateUI(data);
  }, 1000); // Poll every second
}

Polling creates unnecessary server load and network traffic. Each request includes full HTTP headers (typically 500+ bytes), and responses arrive with inherent delay.

WebSocket eliminates polling:

const ws = new WebSocket('wss://api.example.com/realtime');
ws.onmessage = (event) => {
  const data = JSON.parse(event.data);
  updateUI(data); // Instant updates
};

For detailed comparison of REST and WebSocket patterns, see WebSocket vs HTTP.

Decision Guide: When to Use WebSocket vs gRPC

Choose WebSocket when:

1. Browser-based real-time applications - Chat, collaboration tools, live dashboards
2. High-frequency, low-latency messaging - Gaming, financial trading, live sports
3. Simple bidirectional communication - No need for complex RPC semantics
4. Flexible message formats - Want freedom to use JSON, MessagePack, or custom protocols
5. Minimal deployment complexity - No need for proxies or additional infrastructure
6. Mobile apps with WebSocket support - React Native, Flutter web views

Example use cases:

• Real-time chat applications
• Live collaborative editing (Google Docs-style)
• Gaming servers
• Live streaming dashboards
• IoT device communication

Choose gRPC when:

1. Microservices architecture - Service-to-service communication
2. Polyglot systems - Multiple programming languages with shared contracts
3. Strongly typed contracts - Need enforced schemas and code generation
4. Multiple streaming patterns - Need unary, server, client, or bidirectional streams
5. Backend-only communication - No browser clients involved
6. Performance with structure - Want binary efficiency plus type safety

Example use cases:

• Internal microservices communication
• Backend data pipelines
• Multi-language distributed systems
• Mobile apps (native, not web)
• Server-to-server event streaming

Hybrid Approach

Many architectures use both:

Browser Clients
    ↓ WebSocket
Frontend Gateway
    ↓ gRPC
Backend Microservices (gRPC mesh)

This combines WebSocket’s browser compatibility with gRPC’s efficiency for backend communication.

Comparison with Server-Sent Events

Both WebSocket and gRPC support bidirectional streaming, unlike Server-Sent Events (SSE) which only enables server-to-client communication. If you only need server push without client messages, SSE offers a simpler alternative.

For a detailed comparison of unidirectional vs bidirectional protocols, see WebSocket vs SSE.

Frequently Asked Questions

Can I use gRPC over WebSocket?

While technically possible to tunnel gRPC over WebSocket, it’s not recommended. This approach combines the complexity of both protocols without gaining significant benefits. If you need browser support, use gRPC-Web with a proxy. If you need WebSocket’s simplicity, use WebSocket directly with Protocol Buffers for efficient serialization.

Is gRPC faster than WebSocket?

Neither is universally faster - performance depends on your use case. For simple, high-frequency messaging, WebSocket typically has lower latency due to minimal framing overhead. For complex applications with many concurrent streams, gRPC’s HTTP/2 multiplexing and flow control can provide better overall throughput. Binary serialization (Protocol Buffers) performs similarly whether used with gRPC or WebSocket.

Can WebSocket replace gRPC for microservices?

WebSocket can work for microservices, but gRPC offers significant advantages: strongly typed service contracts, automatic code generation in multiple languages, built-in deadlines and cancellation, sophisticated load balancing, and rich ecosystem tooling. Unless you have specific requirements that mandate WebSocket, gRPC is generally the better choice for backend microservices communication.

How do WebSocket and gRPC handle reconnection?

Neither protocol provides automatic reconnection at the protocol level - both require application-level reconnection logic. WebSocket exposes connection state through onclose events, while gRPC provides connection state callbacks. Both require implementing exponential backoff, state recovery, and message replay mechanisms in your application code. Many WebSocket and gRPC client libraries offer built-in reconnection helpers.