Preview of Vue 3.6 & Vapor Mode – Insights from Evan You’s Vue.js Nation 2025 Talk

This article is based on Evan You's talk at Vue.js Nation 2025, titled "Preview of Vue 3.6 & Vapor Mode." In this session, Evan discussed what's new in Vue.js 3.6 with an exclusive preview of its latest features, including the much-anticipated Vapor Mode.

Introduction to Vue 3.6 and Vapor Mode

Evan You started his talk by highlighting significant updates and improvements in Vue.js 3.6 aimed at enhancing developer experience and performance. The introduction of new features like Vapor Mode is set to revolutionize how developers interact with the framework, offering more flexibility and efficiency. Vue Vapor is a variant of Vue that offers rendering without the Virtual DOM, and its creators are Evan you and Kevin Dang, while the most active contributors are: Rizumu Ayaka (also a speaker at Vue.js Nation 2025), Ubugeeei and Doctor Wu.

Vue 3.6: Reactivity Performance Improvements

"The first, foremost, and most important thing is a massive reactivity performance improvement." ~ Evan You

Vue 3.6 is set to deliver significant enhancements in its reactivity performance. This advancement continues the trend from previous versions like Vue 3.4 and 3.5, focusing on optimizing the core reactivity system. The reactivity model in Vue has evolved over time, with its roots going back to the first version. With Vue 3, a major refactor introduced proxy-based reactivity built on top of essential primitives like refs, shadow refs, computed properties, and reactive effects.

Comparison with Other Frameworks and Future Potential

Vue's approach aligns with many modern frameworks that utilize a similar concept known as "signals." This model is increasingly seen as ideal for front-end development due to its ability to describe declarative state relationships effectively. There's even an initiative at TC39 to standardize signals within the language itself, although such standardization is still years away from being realized.

As Evan mentioned, Vue.js continues to innovate with each release, and version 3.6 promises substantial improvements in reactivity performance that align well with contemporary development paradigms. Keep an eye out for future updates that might leverage standardized signals for even greater efficiency.

Understanding Vapor Mode

Vapor Mode is an innovative strategy that significantly enhances the rendering performance of Vue. With this mode, developers can use the same source code but achieve different and more efficient compilation outputs. This means that without learning anything new, you can enjoy improved performance and reduced memory usage while maintaining the same API.

One of the standout features of Vapor Mode is its ability to boost Vue's rendering performance to match that of Solid.js, a framework renowned for its exceptional rendering efficiency.

Achieving Solid.js Level Performance

"It allows Vue's rendering performance to reach the level of Solid JS." ~ Evan You

Compatibility and Flexibility

Vapor Mode is designed with compatibility in mind. It works seamlessly with existing codebases, allowing developers to selectively opt into this mode for performance-sensitive parts of their applications. This flexibility supports piecemeal migration and ensures a smooth integration process.

Evolution of Rendering Strategies in Vue.js

Understanding Vapor Mode also involves looking at how Vue's rendering strategies have evolved:

• **Vue 1:** Utilized a DOM-based templating strategy which involved creating real DOM nodes and establishing reactive bindings on them.
• **Vue 2:** Transitioned to a pure virtual DOM approach, enabling server-side rendering but introducing some memory overhead.
• **Vue 3:** Enhanced virtual DOM with a more powerful compiler that allows better runtime performance through static analysis and optimized code generation.

Despite these advancements in Vue 3, limitations remain due to inherent overheads associated with virtual DOMs. Vapor Mode represents a significant leap forward in how Vue handles rendering. It offers improved performance without sacrificing compatibility or requiring new learning curves for developers.

Vapor Mode Development and Integration

Vapor Mode is an innovative feature in Vue.js 3.6 aimed at enhancing performance by eliminating the virtual DOM. Instead, it generates code that is as close as possible to the optimized code one might write manually. This shift is intended to simplify the runtime and reduce potential pitfalls associated with complex optimization paths.

Development Progress of Vapor Mode

Initially developed in a separate repository named "View Vapor" to facilitate rapid iteration without cluttering the main repo, Vapor Mode has now been integrated into the Vue core repository under a massive pull request with hundreds of commits. This integration allows for better alignment with existing infrastructure and continuous integration pipelines.

Component Model Improvements

A significant focus has been on optimizing component instantiation costs by redesigning component prop slots handling for lazy initialization. This approach has led to substantial performance improvements, allowing for rapid mounting of up to one hundred thousand components in just one hundred milliseconds.

Integration into Vue Core

The integration strategy allows for a mixed component tree comprising both virtual DOM and Vapor components. This flexibility means applications can benefit from Vapor's performance advantages for specific sub-trees while maintaining compatibility with existing virtual DOM components.

Ecosystem Updates, Void(0), Rolldown 1.0 and More

Rolldown has been shipped in its Rolldown 1.0 beta version as of December 2024. It's positioned as a powerful replacement for existing tools like Rollup and esbuild.

The tool is particularly effective when handling large-scale projects and its performance benchmarks highlight a significant speed advantage over competitors like esbuild and Rust-based bundlers.

Performance Benchmarks and Comparisons

Rolldown’s speed is noteworthy:

• At least three times faster than other Rust bundlers.
• Generally faster than esbuild (tested on Linux machines with many cores).

A key highlight is Rolldown’s WebAssembly build performance. It excels in browser environments like StackBlitz (web containers), bundling modules significantly faster than esbuild.

Future Roadmap and Goals for Rolldown

The future roadmap for Rolldown includes several exciting developments:

• Ecosystem CI Compatibility: Aiming to pass more tests to ensure robustness across different environments.

  

• Full Bundle Mode: Addressing startup performance issues with dev servers.

• Module Federation: A sought-after feature by many users currently using Webpack.

• Rolldown-powered Environment APIs: Enhancing server-side rendering (SSR) by replacing JS-based transforms with Rust for better performance in full-stack apps.

The roadmap is ambitious but promises significant enhancements for developers using Rolldown in their projects.

Conclusion

Vue.js 3.6 introduces groundbreaking advancements that promise to elevate the framework's performance and developer experience. With the introduction of Vapor Mode, developers can achieve unparalleled rendering efficiency without altering their existing codebases. This mode, alongside the significant reactivity performance improvements, positions Vue.js as a leader in modern front-end development.

The integration of Vapor Mode into Vue core signifies a pivotal shift in rendering strategies, offering a seamless blend of compatibility and performance. Meanwhile, ecosystem tools like Rolldown are set to redefine project bundling with their impressive speed and efficiency.

As Vue.js continues to innovate, developers are encouraged to explore these new features and contribute to their evolution. Whether you're optimizing existing applications or starting new projects, Vue 3.6 offers a robust foundation for building high-performance, scalable web applications. Keep an eye on future updates and consider diving into the exciting world of Vapor Mode and Rolldown to fully leverage the capabilities of Vue.js 3.6.