What is difference between vue 2 and vue 3

What is difference between vue 2 and vue 3

Vue.js has become one of the most popular JavaScript frameworks in recent years, known for its simplicity and flexibility. With the release of Vue.js 3, there have been significant changes and improvements made to the framework. In this article, we will explore the main differences between Vue 2 and Vue 3, and understand how they impact developers and their projects.

One of the key differences in Vue 3 is the restructured and optimized rendering mechanism. Vue 3 introduces a new component called the Composition API, which allows developers to organize their code in a more modular and reusable way. This new API provides better composition capabilities, making it easier to manage complex state and logic within components. Additionally, Vue 3 has improved the performance of rendering, making applications faster and more efficient.

Another important difference is the partial reactivity system in Vue 3. Unlike Vue 2, which uses a deep reactivity system, Vue 3 introduces the concept of “reactive primitives” and “ref”. Reactive primitives are objects that can be used with the reactivity system, while “ref” allows developers to create reactive references to values that can be accessed and modified. This new reactivity system provides better performance and a more intuitive way of managing reactive data.

Finally, Vue 3 has also made improvements to the overall size and bundle size of the framework. The runtime of Vue 3 is now more tree-shaking friendly, allowing for better optimization of the final bundle size. The modular structure of Vue 3 also makes it easier to import only the necessary features, reducing the overall size of the framework. These improvements make Vue 3 a more efficient and lightweight option for developers.

In conclusion, Vue 3 brings significant improvements to the Vue.js framework, including a restructured rendering mechanism, a new and improved reactivity system, and optimizations in size and bundle size. These changes make Vue 3 a powerful and efficient choice for developers looking to build modern and performant web applications.

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Difference Between Vue 2 and Vue 3: An In-Depth Comparison


Vue.js is a popular JavaScript framework used for building user interfaces. Vue 2 and Vue 3 are two major versions of Vue.js, each with its own set of features and improvements. In this article, we will explore the differences between Vue 2 and Vue 3 to help you understand which version might be the best fit for your needs.

Reactivity System

One of the key differences between Vue 2 and Vue 3 is the reactivity system. Vue 2 uses an object-based observation system, where it defines getters and setters on objects to track changes. Vue 3, on the other hand, uses a proxy-based system, which allows for more efficient reactivity and better performance. With the proxy-based system, Vue 3 is able to observe changes at a more granular level, resulting in better performance and reduced memory usage.

Composition API

The Composition API is another major difference between Vue 2 and Vue 3. The Composition API in Vue 3 provides a new way to organize and reuse logic in Vue components. It allows developers to define component logic with functions, making it easier to share and reuse code across components. In contrast, Vue 2 uses the Options API, which can sometimes lead to code duplication and make it harder to understand and maintain complex components.


Vue 3 introduces several performance improvements over Vue 2. With its new reactivity system and optimized rendering, Vue 3 is generally faster than Vue 2. The proxy-based reactivity system in Vue 3 reduces the overhead of object property access, resulting in faster rendering and improved overall performance. Additionally, Vue 3 introduces a new static tree hoisting optimization, which further improves performance by reducing redundant updates to components.

Bundle Size

In terms of bundle size, Vue 3 is slightly larger than Vue 2 due to the new features and improvements it offers. However, the difference in bundle size is not significant and is outweighed by the performance benefits and new capabilities provided by Vue 3.

Transition from Vue 2 to Vue 3

If you are currently using Vue 2 and considering upgrading to Vue 3, there are some important points to consider. While Vue 3 offers many improvements, it is not fully backward compatible with Vue 2. This means that some changes may be required in your existing codebase when migrating to Vue 3. The Vue team provides a migration guide and tooling to help developers with the transition process.


Vue 2 and Vue 3 are both powerful versions of Vue.js with their own unique set of features and improvements. Vue 3 introduces a more efficient reactivity system, the Composition API for better code organization and reuse, and various performance enhancements. While there may be some challenges in migrating from Vue 2 to Vue 3, the benefits outweigh the costs for many developers. Ultimately, the choice between Vue 2 and Vue 3 depends on your specific project requirements and preferences.

Major Changes in Vue 3

1. Composition API

The most significant change in Vue 3 is the addition of the Composition API. This new API provides developers with a more flexible way to organize and reuse code. With the Composition API, you can define component logic using functions, making it easier to separate concerns and create reusable logic that can be easily shared between components.

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The Composition API also allows for more fine-grained control over the lifecycle of components, improving performance and reducing the complexity of managing component state.

2. Better TypeScript Support

Vue 3 has improved support for TypeScript, making it easier to write type-safe Vue applications. The new version introduces better type inference, which means you’ll get more accurate type checking and improved autocompletion.

Additionally, Vue 3 includes new TypeScript-specific APIs that enhance the development experience for TypeScript users. These APIs provide better type inference for reactive properties and improved type checking for component options.

3. Enhanced Reactivity System

The reactivity system in Vue 3 has been completely rewritten to improve performance and provide better reactive behavior. The new system, called the “Proxy-based reactivity system,” is based on JavaScript’s Proxy API.

This new reactivity system provides better reactivity tracking, allowing Vue to detect and track changes to reactive properties more efficiently. It also improves the reactivity behavior of arrays, making it easier to handle array mutations.

4. Optimized Virtual DOM

Vue 3 introduces an optimized Virtual DOM that improves rendering performance. The new Virtual DOM uses a static tree structure, which eliminates the need to traverse the entire component tree during each update.

This optimization leads to faster rendering and better overall performance, especially in large applications with complex component hierarchies.

5. Tree-Shaking Support

Vue 3 includes improved tree-shaking support, which means that unused features and components are automatically stripped out during the build process. This can significantly reduce the size of your final bundled JavaScript files, improving page load times.

The improved tree-shaking support also allows for better code organization and encourages developers to write modular and reusable code.

6. Breaking Changes

6. Breaking Changes

While Vue 3 brings many improvements, it also introduces some breaking changes compared to Vue 2. These changes include modifications to the component lifecycle, different syntax for custom directives, and updates to the way props are defined and used. It’s important to carefully review the Vue 3 migration guide and update your code accordingly when transitioning from Vue 2 to Vue 3.

Improved Performance in Vue 3

In Vue 3, significant improvements have been made to enhance the performance of the framework. These optimizations aim to make Vue applications faster and more efficient, providing a better user experience.

1. Compiler Improvements

The compiler in Vue 3 has been rewritten to generate more optimized code. It is now able to produce smaller bundle sizes, resulting in faster loading times for Vue applications. The new compiler also provides better TypeScript support and improved error handling.

2. Virtual DOM Improvements

In Vue 3, the Virtual DOM algorithm has been optimized to reduce memory usage and enhance rendering performance. The reactivity system has been rewritten to be more efficient, resulting in faster updates and reduced overhead.

3. Composition API

The introduction of the Composition API in Vue 3 allows developers to write more efficient and performant code. The Composition API encourages code reuse and better separation of concerns, leading to improved performance. It also enables better tree shaking, allowing unused code to be eliminated during the build process, resulting in smaller bundle sizes and faster loading times.

4. Fragments

In Vue 3, fragments have been introduced as a new feature. Fragments allow developers to group multiple elements together without the need for a wrapper element. This reduces unnecessary nesting, resulting in improved rendering performance.

5. Optimized Reactivity

The reactivity system in Vue 3 has been optimized to reduce the number of unnecessary re-renders. This optimization improves the performance of reactive updates, resulting in faster rendering speed and reduced overhead.

6. Tree Shaking

With Vue 3, the tree shaking capabilities have been improved. Tree shaking is a process where unused code is eliminated during the build process, resulting in smaller bundle sizes and faster loading times. This optimization helps to improve the overall performance of Vue applications.

7. SFC (Single File Component) Improvements

The Single File Component (SFC) format has been improved in Vue 3. The new format provides better TypeScript support, improved error handling, and enhanced tooling integration. These improvements make it easier for developers to work with Vue components and contribute to improved performance.

Overall, the performance improvements in Vue 3 make it a highly efficient and performant framework for building web applications. Developers can expect faster loading times, improved rendering speed, and enhanced overall performance when using Vue 3.

Composition API in Vue 3


The Composition API is one of the most significant new features introduced in Vue 3. It offers an alternative way of structuring and organizing your Vue components, departing from the traditional Options API.

Benefits of using the Composition API

The Composition API provides several benefits over the Options API:

  • Modularity: The Composition API allows you to encapsulate and reuse logic in modular functions or hooks, making your code more maintainable and organized.
  • Improved Type Safety: With the Composition API, TypeScript integration is more seamless and provides better type inference for reusable logic.
  • Code Organization: The Composition API encourages a more declarative and intuitive way of defining your component’s logic, separating concerns into smaller functions or hooks.
  • Reactivity: Vue’s reactivity system is fully supported in the Composition API, allowing you to create reactive variables and computed properties with ease.


To use the Composition API in Vue 3, you need to import the necessary functions from the core Vue package:

import { ref, reactive, computed, watchEffect } from 'vue';

Here are some key functions and concepts in the Composition API:

  • ref: Creates a reactive variable that can be used in your template or computed properties.
  • reactive: Creates a reactive object that allows you to define reactive properties.
  • computed: Creates a computed property that recalculates its value automatically whenever its dependencies change.
  • watchEffect: Allows you to define reactive side effects that will run whenever any reactive dependencies change.


Here’s a simple example demonstrating the usage of the Composition API:

import { ref } from 'vue';
export default {
setup() {
// Define a reactive variable
const count = ref(0);
// Define a method that increments the count
const increment = () => {
return { count, increment };

In the example above, we define a reactive variable called “count” using the ref function. We also define a method called “increment” that increments the count value. The setup function returns an object with both the count and increment variables, which can be used in the template or computed properties.

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The Composition API in Vue 3 offers a more modular, organized, and flexible way of structuring your Vue components. It encourages a declarative and intuitive approach to writing component logic, enhancing code maintainability and reusability. With its built-in reactivity system and TypeScript support, the Composition API provides a powerful toolset for building robust Vue applications.

Modular Architecture in Vue 3

In Vue 3, modular architecture is a key concept that allows developers to organize their code into reusable and self-contained modules. This approach promotes code maintainability, reusability, and scalability.

Benefits of Modular Architecture

  • Code organization: Modular architecture helps in breaking down a complex application into smaller and manageable modules. Each module focuses on a specific functionality or feature, making it easier to understand and maintain the codebase.
  • Reusability: Modules in Vue 3 can be easily reused across different projects or within the same project. This decreases development time and effort as developers do not need to reinvent the wheel for every task.
  • Scalability: Modular architecture allows for easy scalability as new modules can be added or existing modules can be modified without impacting other parts of the application. This flexibility enables developers to quickly adapt to changing business requirements or user needs.

Modular Techniques in Vue 3

Vue 3 provides several techniques and features that facilitate modular architecture:

  1. Composition API: The Composition API in Vue 3 allows developers to organize their code logic into reusable functions, called composition functions. These functions can be easily shared and composed together to create complex behaviors. This promotes code reusability and modularity.
  2. Components: Vue 3’s component system helps in creating reusable UI components that can be easily shared and composed in different parts of the application. This encourages modularity by separating concerns and promoting component reusability.
  3. Dynamic Imports: Vue 3 supports dynamic imports, which allow developers to load modules on-demand. This helps in reducing the initial bundle size and improving the overall performance of the application. Dynamic imports enable developers to split their code into smaller chunks and load them only when required.
  4. Module Federation: Vue 3 integrates with Module Federation, a webpack feature that allows for sharing code between multiple applications. This enables developers to build micro-frontends and share modules across different Vue projects. Module Federation promotes code reuse and modularity across a distributed architecture.


Modular architecture is an important aspect of Vue 3 that helps developers build scalable, maintainable, and reusable applications. With features like the Composition API, component system, dynamic imports, and Module Federation, Vue 3 provides a robust foundation for developing modular applications.

By adopting modular architecture practices, developers can improve code organization, increase reusability, and easily scale their Vue 3 projects. This ultimately leads to more efficient development processes and better user experiences.

Intrinsic Element Attributes in Vue 3

Vue 3 introduces a new way to handle intrinsic element attributes. Intrinsic elements are HTML elements like <div>, <p>, or <span> that are native to the browser and don’t require any special handling by Vue.

New Syntax

In Vue 2, in order to add attributes to intrinsic elements, you had to use the v-bind directive. This would look like:

<div v-bind:class="{'red': isRed}"></div>

In Vue 3, the new composition API allows you to use a more concise syntax to add attributes to intrinsic elements. You can simply add the attribute directly to the element, just like in regular HTML:

<div :class="{'red': isRed}"></div>

This new syntax makes it easier to work with intrinsic elements and reduces the verbosity of the code.

Usage with Components

The new syntax for intrinsic element attributes can also be used inside Vue components. For example, if you have a custom Button component, you can pass attributes to it using the new syntax:

<Button :disabled="isDisabled">Click me</Button>

Note that the attribute name is prefixed with a colon (:) to indicate that it is a binding and not a static value.

Handling Events

The new syntax for intrinsic element attributes also extends to event handling. In Vue 2, you would use the v-on directive to handle events on intrinsic elements:

<button v-on:click="onClick">Click me</button>

In Vue 3, you can use the new event handling syntax with intrinsic elements as well:

<button @click="onClick">Click me</button>

This syntax is more intuitive and consistent with how event handling is done in JavaScript and other frameworks.


The new syntax for intrinsic element attributes in Vue 3 offers a more concise way to add attributes and handle events on native HTML elements. It simplifies the code and makes it easier to work with both intrinsic elements and components.

By leveraging the new composition API and the improved syntax, developers can write cleaner and more maintainable code in Vue 3.

TypeScript Support in Vue 3

Vue 3 comes with built-in TypeScript support, making it easier for developers to write type-safe Vue applications. Here are some key features and benefits of TypeScript support in Vue 3:

1. Improved Type Inference

With TypeScript in Vue 3, the compiler is able to provide better type inference for props, data, computed properties, and even lifecycle hooks. This helps catch potential type errors during development and provides better IntelliSense support in code editors.

2. Stronger Component Validation

TypeScript allows developers to define interfaces for components, making it easier to validate component props and emit events with correct data types. This helps catch errors and prevents runtime issues related to incorrect prop usage.

3. Composition API with TypeScript

Vue 3’s Composition API, which provides a more flexible way to organize and reuse logic in components, fully supports TypeScript. This means you can define your composition functions with type annotations and benefit from improved IntelliSense and type safety.

4. Type-Checked Templates

Vue 3’s template syntax also benefits from TypeScript support. The Vue compiler can analyze template expressions and provide type checking, ensuring that data binding and computed properties are used correctly.

5. Better IDE Integration

TypeScript support in Vue 3 improves integration with popular code editors like Visual Studio Code. The editor can provide real-time error highlighting, code completion, and other useful features based on TypeScript’s type information.

Overall, TypeScript support in Vue 3 enhances the development experience by providing better type safety, improved tooling support, and easier component validation. It allows developers to catch potential errors early and write more maintainable and robust Vue applications.

Reactivity System in Vue 3


In Vue 3, the reactivity system has been significantly revamped to improve performance and flexibility. The reactivity system is responsible for automatically updating the user interface when the underlying data changes.

Proxy-based Reactivity

Vue 3 uses a proxy-based reactivity system instead of the previously used Object.defineProperty method in Vue 2. Proxies allow for more fine-grained reactivity and better performance.

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Reactive Objects

In Vue 3, objects can be made reactive using the reactive() function. When an object is made reactive, any changes to its properties will be automatically tracked, and the user interface will be updated accordingly.

Reactive Arrays

Arrays can also be made reactive in Vue 3 using the ref() function. When an array is made reactive, any changes to its length or its individual elements will be automatically tracked and reflected in the user interface.

Reactivity Caveats

There are some caveats to keep in mind when using the reactivity system in Vue 3. For example, reactive objects must be accessed using reactive() or ref() functions to ensure reactivity. Also, properties added to an object after it has been made reactive will not be reactive by default.

Composition API

In Vue 3, the reactivity system is tightly integrated with the new Composition API. The Composition API allows for more flexible and modular component composition by providing a set of functions to access and manipulate reactive data.


The reactivity system in Vue 3 offers improved performance and flexibility compared to Vue 2. By using proxies and the reactive() function, objects and arrays can be made reactive and automatically update the user interface when their properties change.

Compatibility with Existing Vue 2 Codebases

One of the most important considerations when transitioning from Vue 2 to Vue 3 is the compatibility with existing Vue 2 codebases. Vue 3 is designed to be a progressively adoptable upgrade, which means that existing Vue 2 codebases can still work in Vue 3 with minimal modifications.

Breaking Changes

While Vue 3 strives to maintain a high level of compatibility with Vue 2, there are several breaking changes introduced in Vue 3 that may require modifications to existing codebases:

  • The new Composition API: Vue 3 introduces a new Composition API, which provides a different way of organizing and reusing code compared to the Options API used in Vue 2. Existing Vue 2 codebases that heavily rely on the Options API will need to be refactored to use the Composition API.
  • Modified component lifecycle hooks: Vue 3 introduces changes to several component lifecycle hooks, such as the removal of the beforeMount and beforeUpdate hooks, and the addition of the beforeUnmount hook. Existing codebases will need to update their lifecycle hooks accordingly.
  • Changes to global configurations: Vue 3 introduces changes to global configurations, such as the removal of the silent mode and the addition of the compilerOptions. Existing codebases that modify global configurations will need to update their code accordingly.

Migration Strategies

To ensure a smooth transition from Vue 2 to Vue 3, the Vue team provides several tools and resources. These include:

  1. The Vue 2 to Vue 3 migration build: The Vue team provides a migration build that assists in identifying compatibility issues and provides suggestions for migration. This build can be added to existing Vue 2 codebases to help with the transition.
  2. The “vue-migration-helper” package: This package provides a command-line tool that can automatically fix common migration issues in Vue 2 codebases. It can handle tasks such as updating component imports and fixing breaking changes in lifecycle hooks.
  3. The official Vue 2 to Vue 3 migration guide: The Vue team provides a comprehensive migration guide that covers the necessary steps to upgrade from Vue 2 to Vue 3. The guide includes detailed explanations, code examples, and migration strategies for different scenarios.


While there are some breaking changes introduced in Vue 3, the Vue team has made efforts to ensure compatibility with existing Vue 2 codebases. By following the recommended migration strategies and utilizing the provided tools and resources, developers can smoothly transition their Vue 2 projects to Vue 3.


What are the main differences between Vue 2 and Vue 3?

The main differences between Vue 2 and Vue 3 are the improved performance and enhanced developer experience. Vue 3 introduces a new reactivity system that is significantly faster than the one used in Vue 2. It also brings a more flexible and powerful composition API, allowing developers to write cleaner and more modular code. In addition, Vue 3 introduces several new features and improvements, such as teleport, fragments, and the ability to mount components on a text node.

Is it easy to migrate from Vue 2 to Vue 3?

Migrating from Vue 2 to Vue 3 can require some manual changes, but overall, the process is relatively straightforward. Vue 3 provides a migration build that helps identify compatibility issues and provides warnings for deprecated features. The official Vue 3 documentation also provides a migration guide that details the required changes. In general, the migration process involves updating the syntax and adapting the code to the new features and APIs introduced in Vue 3.

Can I still use Vue 2 plugins in Vue 3?

No, Vue 2 plugins are not directly compatible with Vue 3. However, many popular Vue 2 plugins have already been updated to work with Vue 3. If you rely on a specific Vue 2 plugin, you should check the plugin’s documentation or GitHub repository to see if a Vue 3 compatible version is available. If not, you may need to find an alternative plugin or explore other options for achieving the desired functionality in Vue 3.

Are there any breaking changes in Vue 3?

Yes, there are some breaking changes in Vue 3. The major ones include the removal of filters, the introduction of the new reactivity system, changes to the component registration syntax, and updates to the v-model directive. There are also some changes to the lifecycle hooks and the way directives are used. The Vue 3 documentation provides a comprehensive list of all the breaking changes and how to migrate your code to adapt to these changes.

What are the benefits of using Vue 2?

Vue 2 is a mature and stable version of the framework that has been extensively used and tested by the community. It has a large ecosystem with many available plugins and libraries. Vue 2 also has good documentation and a wide range of learning resources. If you have an existing Vue 2 project, there may not be a need to upgrade to Vue 3 immediately, especially if you don’t require the specific features and improvements introduced in Vue 3.

What are the benefits of using Vue 3?

Vue 3 brings significant improvements in performance, developer experience, and maintainability. The new reactivity system in Vue 3 is faster, making your application more responsive. The composition API allows for more modular and reusable code, making it easier to develop and maintain complex applications. Vue 3 also introduces new features like teleport and fragments, which enhance the flexibility and power of Vue components. Overall, Vue 3 offers a more modern and efficient development experience.