Web Workers are a browser feature that allows you to run JavaScript code in the background, separate from the main browser thread. They enable concurrent execution and help prevent blocking the user interface during computationally intensive or time-consuming tasks. Here are some key points about web workers: 1. Background Execution: Web Workers allow you to run scripts in the background without blocking the main thread. This keeps the user interface responsive and improves overall performance. 2. Separate Thread: Web Workers run in a separate thread from the main JavaScript thread, often referred to as the "worker thread." This thread is isolated and doesn't share the same memory space as the main thread. 3. Communication: Web Workers communicate with the main thread using messaging. They can receive messages from the main thread and post messages back to it. This messaging system allows data exchange and coordination between the worker and the main thread. 4. Limited Scope: Web Workers have limited access to browser APIs and the DOM. They can't directly manipulate the DOM or access certain objects and methods available in the main thread. This limitation helps maintain security and prevents worker threads from interfering with the user interface. 5. Types of Web Workers: There are two types of web workers: dedicated workers and shared workers. Dedicated workers are tied to a specific script and can communicate only with the script that created them. Shared workers can be accessed by multiple scripts or web pages running on the same origin, allowing them to share data and communicate with multiple sources. Web Workers are useful for various tasks such as heavy computations, parsing large datasets, performing complex algorithms, and offloading non-UI tasks. They can help improve the overall responsiveness and performance of web applications by distributing the workload across multiple threads. Here's a simple example of using a web worker:

// main.js (main thread)
const worker = new Worker('worker.js');

worker.onmessage = function(event) {
  console.log('Message from web worker:', event.data);

worker.postMessage('Hello from main thread!');

// worker.js (worker thread)
self.onmessage = function(event) {
  console.log('Message from main thread:', event.data);
  self.postMessage('Hello from web worker!');

In this example, the main thread creates a web worker using the `Worker` constructor, specifying the script file (`worker.js`). The main thread sends a message to the web worker using `worker.postMessage()`. The web worker receives the message in its `onmessage` event handler, logs it, and sends a response back to the main thread using `self.postMessage()`. The main thread receives the response in its `onmessage` event handler and logs it. Web Workers are supported in modern browsers and provide a powerful tool for performing background tasks, improving performance, and enhancing the user experience of web applications.