Top 30 LWC Interview Questions In 2026

Salesforce introduced Lightning Web Components globally in 2018. The motive for launching this interesting framework in the software industry is to ease developers’ work by leveraging Salesforce Lightning components. Lightning Web Components (LWCs) are built with JavaScript and basic HTML. 

It helps strengthen modules, custom elements, and more. There is no doubt that, due to high market demand, there are massive opportunities for Salesforce LWC developers. We know the competition for this position is high in the industry. That’s why we have compiled these top LWC interview questions to make your journey easier.

LWC Interview Questions for Freshers

If you are starting your journey as an LWC developer, reading this set of basic Salesforce LWC interview questions will help you. 

1. What is LWC?

Lightning web components (LWC) is a modern framework that builds user interfaces by using standard web technologies like JavaScript and HTML. It helps developers create reusable, effective, and efficient components that can improve the performance of Salesforce applications. LWC also provides an enhanced development experience, improved performance, and strong cross-browser and device compatibility.

2. How is Aura different from Lightning Web Components?

Aura and LWC are both frameworks used for building components in the Salesforce ecosystem, but they have some major differences: 

• Aura is a proprietary framework, while Lightning web components use standard web technologies such as JavaScript, HTML, and CSS.
• LWC generally performs better than Aura due to its native web standards and effective rendering. 
• Aura is proprietary, so developers must have sufficient experience before using it. On the other hand, LWC is easy to learn and helps developers become familiar with standard web technologies.  

3. What do you mean by Salesforce Lightning? 

Salesforce Lightning is a component-based framework useful for Salesforce application development. Its primary objective is to ease development for developers with limited programming experience. It includes: 

• The Lightning Component Framework and the Lightning App Builder help create applications using drag-and-drop features. 
• Lightning Experience, which is a modern UI that replaces the Salesforce Classic interface. 

4. What is the use of Lightning Components Framework? 

The Lightning component framework is a UI framework helpful for developing responsive, dynamic applications for desktop and mobile users.  

5. Mention some Lightning Salesforce Components.

There are multiple components in Salesforce Lightning, such as:

1. Lightning Button
2. Lightning Input 
3. Lightning Record Form 
4. Lightning File Upload
5. Lightning Card
6. Lightning Layout 
7. Lightning Accordion
8. Lightning Datatable

6. What is renderedCallback() in LWC? 

The “renderedCallback()” is the function or method in LWC that executes the logic once the component completes its rendering phase. This lifecycle hook is important for performing actions after the component is rendered, such as manipulating the DOM (Document Object Model) and initializing third-party libraries. 

7. What is the use of @Wire in Lightning Web Components? 

The @wire decorator in LWC associates a property or method with a Salesforce data source. It automatically manages data collection, error handling, and state management, making it easier to integrate Salesforce data into components. The @wire decorator is compatible with Apex methods and Salesforce’s built-in wire adapters.

8. Name the tools present in Salesforce Lightning. 

Salesforce Lightning includes the Lightning Component Framework, Lightning App Builder, Lightning Process Builder, Lightning Design System, Lightning Component Library, and Lightning Connect, which are useful tools. 

9. What is Lightning Process Builder?

Lightning Process Builder is a visual tool for automating business processes and workflows within Salesforce. It offers a user-friendly interface for creating complex processes using a point-and-click approach, allowing you to perform operations such as changing records, sending emails, and running Apex programs without writing any code.

10. What is the use of SFDX?

SFDX stands for “Salesforce Developer Experience.” This tool is useful because it improves developers’ experience working on the Salesforce platform. 

11. What is meant by cacheable = True Annotations?

When you set cacheable = true, the function can only get data and cannot perform any data manipulation language (DML) actions. It is used to improve component performance by displaying cached data from client-side storage rather than making a server trip. To refresh obsolete Apex data, we must use refreshApex because LDS (Lightning Data Service) does not handle Apex data (in the case of a wired service).

12. When is the Property or Wire Method called in the Component Lifecycle? 

Wire methods or properties are called whenever a reactive parameter changes or the component is initialized. The @wire decorator ensures automated updates and data fetching. 

13. What are Lifecycle Hooks in LWC? 

In LWC, lifecycle hooks are callback methods that execute at specific stages of a component’s creation, rendering, and removal from the DOM. They help you run custom logic during the component’s lifecycle.

LWC supports the following lifecycle hooks:

Constructor: Called when the component has been generated. It is the first lifecycle hook to fire and is used for component initialization. 

• Constructor: Called when the component has been generated. It is the first lifecycle hook to fire and is used for component initialization. 

• ConnectedCallback: This callback is triggered when the component is added to the document. 

• RenderedCallback:  Called after each render of the component. This lifecycle hook is specific to Lightning Web Components and is not part of the definition of HTML custom elements. It flows from child to parent and is defined in LightningElement rather than HTMLElement.

• DisconnectedCallback: This function is required when a component is deleted from a document. 

• ErrorCallback: This method is called whenever a descendant component throws an error. The error argument is the JavaScript error object, and the stack argument is a string. This lifecycle hook is specific to LWC and is not part of the definition of HTML custom elements. 

14. Do quick actions support the LWC Components? 

Yes, quick actions support the LWC. Individuals can use Lightning Web Components to generate custom quick actions. However, these components only help on the record pages, list views, and in some cases, utility bars, depending on the action types and where they are deployed. 

15. What do you mean by a Promise in Async Transactions? Also, Name its Different Stages.

A promise is an object returned by an asynchronous transaction that notifies you when the transaction has finished or encountered an error. For example, when you make an urgent call to an apex, it produces a promise object. Depending on the returned object, the execution will either enter the ‘then’ block, indicating a successful transaction, or the ‘catch’ block, indicating a failed transaction.

The stages of a promise are:

• Pending: Awaiting a result.
• Fulfilled: The promise is successful.
• Rejected: The promise has failed.

LWC Interview Questions for Experienced Professionals

As an LWC developer, having prior experience before switching to a new job in the industry will help you. But reading these advanced Salesforce LWC interview questions will prepare you for the next interview round. 

16. What are Web Components? Is the LWC Process Based on Web Components?

Web Components are a set of web platform APIs that enable developers to create reusable, encapsulated HTML tags for custom elements. They consist of the Shadow DOM, Custom Elements, and HTML Templates. LWC is built on Web Components and uses standard APIs to develop fast, flexible, and reusable elements.

17.  What is the Difference between Connectedcallback and Renderedcallback in LWC?

Lifecycle hooks are unique methods in LWC that enable developers to run code at specific stages of a component’s lifecycle. ConnectedCallback and renderedCallback are among the most commonly used lifecycle hooks. These hooks enable developers to execute code when a component is inserted into the DOM and after it has been rendered. Understanding the distinctions between these hooks is essential for efficiently handling component initialization and updates. 

18. Are Callback Functions Asynchronous or Synchronous? 

Callback functions can be synchronous or asynchronous, depending on the context in which they are passed. For example, callbacks in setTimeout() or fetch() are asynchronous, while callbacks in array methods like forEach() are synchronous.

19. What do you mean by Callback Hell?

In simple terms, callback hell refers to the situation where multiple stacked callback functions result in a complex code structure. It frequently occurs in asynchronous programming when callbacks are used extensively, leading to deeply nested code that is difficult to maintain and debug.

20. What are Decorators in LWC? 

There are three decorators for the LWC programming model that add functionality to the functions or properties. 

1. @track
2. @api
3. @wire

21. What is the difference between var and let in JavaScript? 

‘var’ is a function-scoped variable which can be redeclared. On the contrary, ‘let’ is the block-scoped variable that cannot be redeclared within the same scope. 

‘var’ declared variables are hoisted to the top of their scope. On the other hand, ‘let’ variables offer better scoping rules and eliminate the issues related to variable hoisting. 

22. What is LMS? 

The acronym LMS stands for Lightning Message Service. It enables smooth communication among Lightning Web Components, Aura Components, and Visualforce sites. LMS supports message broadcasting and listening across various program areas, facilitating inter-component communication.

23. Are there any Application Events in LWC?

No, LWC does not support the application events used by Aura Components. Rather, LWC communicates with components via a regular DOM event model. Custom Events can be dispatched and listened to, aligning the framework with modern web development practices.

24. What do you mean by String Interpolation?

String interpolation refers to the process of embedding expressions or variables within a string. It is commonly done in JavaScript with template literals, which are indicated by backticks (`).

25. When do we face the Error of “Cannot Assign to Read Only Property” in the Lightning Web Components?

This error occurs when you attempt to assign a value to a read-only property. In LWC, it can occur if you attempt to directly change a public property passed down from a parent component or if you attempt to edit the properties of an immutable object.

26. How can you pass data between the LWC? 

Passing data between components in LWC is a common requirement for creating dynamic, interactive applications. There are multiple ways to do this process, but it depends on the relationship between the components. There are some common methods through which data can be passed between the Lightning Web Components, which include:

Properties: Parent components can send data to child components using public properties marked with @api.

Events: Child components can communicate with parent components by triggering custom events that the parent components can manage.

27. How can you communicate from Child to Parent Component in LWC?

In LWC, communication between a child and a parent component happens through custom events. The child component uses the CustomEvent constructor to dispatch an event, which the parent component then receives and handles.

28. How can you Render Elements in LWC Conditionally? 

LWC supports conditional rendering with template directives such as ‘lwc:if’, ‘lwc:elseif’, and ‘lwc:else’. These directives include or exclude elements of the template depending on the value of a Boolean property.

29. What is the Difference between “===” and “==”?

Both === and == are used to compare two variables. However, == does not consider data types and performs type coercion, meaning the interpreter attempts to automatically transform data types to match the values. On the other hand, === always returns false if the data types are different.

For example:

2 == “2” will return True (type coercion occurs).

2 === “2” returns False (no type coercion).

30. How do you Handle Asynchronous Operations in LWC?

Handling asynchronous operations in Lightning Web Components is essential for tasks such as processing user input, performing background computations, and fetching data from the server. These operations ensure that UI responds when these tasks are completed.

async handleClick() {
  try {
    const result = await getAccountData({ accountId: this.recordId });
    this.data = result;
  } catch (error) {
    this.error = error;
  }
}

Final Word

Preparing for an interview can be challenging, especially for technical roles like Lightning Web Components (LWC) development. These 30 LWC  interview questions are designed to help you revise key concepts, understand real-world applications, and confidently face your next Salesforce LWC interview.

If you are looking to become an LWC developer in 2026, this will be your starting point. Explore LWC training and go from a beginner to a job-ready professional with hands-on projects.