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.

Preparing for a Salesforce LWC interview? Knowing the basics is not enough. Interviewers often ask about real-world development, component communication, Apex, lifecycle hooks, and JavaScript concepts. 

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. In this guide, we have covered important LWC interview questions and answers in simple language. You will learn the core concepts, understand practical examples, and revise the topics that commonly appear in interviews. Ready to test your knowledge?

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 Salesforce’s 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: 

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 used to build reusable and interactive user interfaces on the Salesforce platform. Developers can combine smaller components to create responsive and dynamic applications.

Example: A developer can combine buttons, forms, tables, and other components to create a custom dashboard.

5. What are Lightning Base Components in Salesforce?

Lightning Base Components are prebuilt UI components provided by Salesforce. They are ready-to-use building blocks that help developers create Salesforce applications without building common UI elements from scratch.

Example: Instead of creating a button from scratch with HTML and CSS, you can simply use: 

<lightning-button 

    label=”Save” 

    onclick={handleSave}>

</lightning-button>

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.

Example:

import { LightningElement, wire } from ‘lwc’; 

import getAccounts from ‘@salesforce/apex/AccountController.getAccounts’; 

export default class AccountList extends LightningElement {

 @wire(getAccounts)

 Accounts;

 } 

Here, @wire calls the Apex method and makes the returned data available to the component. 

8. What are the main tools in Salesforce Lightning?

Salesforce Lightning includes several tools that help developers and admins build, customize, design, and automate Salesforce applications. 

• Lightning App Builder – Build custom Lightning pages using a point-and-click interface.
• Lightning Component Framework – Build reusable UI components using LWC or Aura.
• Lightning Component Library – Explore Salesforce’s prebuilt components and their usage. 
• Experience Builder – Create and customize digital experiences using templates and components.
• Flow Builder – Build and automate business processes using a low-code, visual interface.

9. What is Lightning Process Builder? (officially retired)

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 Salesforce Flow Builder?

Flow Builder is a low-code tool for building automated business processes. It lets admins and developers create flows using a visual interface instead of writing code for every automation.

Example: When a new Case is created, a flow can automatically assign it to the right team, update fields, and send a notification. 

11. What is the use of SFDX?📍[Asked at Cyntexa, Round: Technical, Year: 2026]

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

Today, Salesforce uses Salesforce CLI as the main command-line interface for developers.

12. 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).

13. When is the Wired Property or Wired 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. 

For example, if an LWC uses a recordId as a reactive parameter, changing the recordId can cause the wire service to retrieve data for the new record.

14. What are LWC lifecycle hooks and their execution order?

Lifecycle hooks are special methods in LWC that run at the different stages of a component’s lifecycle. They let developers run custom logic when a component is created, added to the DOM, rendered, or removed.
constructor() → connectedCallback() → render() → renderedCallback() → disconnectedCallback() → errorCallback(error, stack).

 Constructor runs on instantiation, connectedCallback when inserted in the DOM, renderedCallback after every component render.

15. Do quick actions support the LWC Components? 

Yes, quick actions support 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. 

For example, an LWC quick action can open a custom form, perform an operation or guide users through a specific task without leaving the record page.

16. What do you mean by a Promise in Async Transactions? What are 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 method, 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.

Read More:

50 Salesforce Interview Questions That Will Get You Hired in 2026

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. 

17. What are Web Components? Is the LWC Process Based on Web Components? 📍[Asked at Cyntexa, Round: Technical, Year: 2025]

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.

18.  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. Both are lifecycle hooks, but they run at different stages of the component lifecycle.

19. Are Callback Functions Asynchronous or Synchronous? 

A callback is simply a function passed to another function. 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.

20. 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.

To avoid callback hell, modern JavaScript provides alternatives such as promises and async/await.

21. What are Decorators in LWC? 

Decorators in LWC are special JavaScript features that add specific behavior to properties and methods. They are also prefixed by the @ symbol. They are used to tell the framework how a property or method should work.

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

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

‘var’ is a function-scoped variable that can be redeclared. On the contrary, ‘let’ is a 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. 

23. Are there any Application Events in LWC?📍[Asked at Cyntexa]

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 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 LWCs? 

Passing data between components in LWC is a common requirement for creating dynamic, interactive applications. There are multiple ways to do this, but it depends on the relationship between the components. There are some common methods through which data can be passed between 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.
• Lightning Message Service: Unrelated or sibling components can communicate through a message channel.
• Shared data services: Components can work with the same record data. 

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.

The child creates an event with CustomEvent and dispatches it using dispatchEvent(). The parent listens for that event and handles the data sent by the child. 

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 the 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;

  }

}

Scenario-based interview questions

31. You need to load Salesforce records when a component loads, but you also need to load data only after a user clicks a button. Would you use @wire or imperative Apex? 

I would choose the approach based on when the data needs to be loaded. If the loading of records occurs when the component is loaded, use @wire, as it is declarative and reactive. It automatically fetches and executes the data as soon as the component is initialized.

If the loading of Salesforce records is done after the user clicks the button, I would use imperative Apex, this gives explicit programming control, allowing you to invoke an Apex method inside a JavaScript event handler function and handle the result via promises.

32. An Apex method successfully updates a record, but your LWC still shows the old data. How would you troubleshoot and fix it? 

LWC shows old data because it is reading from a client-side cache instead of fetching data from the newly updated database. For troubleshooting, I would first check the data source and see whether it loaded correctly through an Apex @wire. To fix it, store the wire response, import the refreshApex helper function into the file, and then call refreshApex after the upgrade.

33. You need to display 10,000 records in a lightning-datatable. The page becomes slow and sometimes freezes. How would you improve the performance? 

Instead of loading all at once, I would render the records in small batches. To improve performance, I can use server-side pagination, lazy loading, or infinite scrolling.
Core performance Strategies are :

• Enable infinite Loading: Use the enable-infinite loading attribute and the onloadmore event handler on the component to fetch and append records in small chunks as the user scrolls. 
• Implement Server-Side Pagination: Use LIMIT and OFFSET clauses in your Apex SOQL queries to retrieve only the subset of data; this avoids heavy load.
• Reduce the column count: This limits the no of visible columns in the data table.
• Add Search and Filtering: Provide search boxes or filter criteria before loading all the data.

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 beginner to job-ready professional with hands-on projects.