What Role Does Browser Rendering Play in Interaction to Next Paint (INP), and How Can I Optimize Rendering Paths to Enhance INP Scores?


Interaction to Next Paint (INP) is a measure of how quickly a webpage responds to user interactions. Browser rendering plays a crucial role in INP, as it affects the speed with which the visual feedback from user interactions appears. Optimizing rendering paths can significantly enhance INP scores. This guide explores practical strategies for improving rendering and boosting INP performance.

Understanding INP and Browser Rendering

What is INP?

Interaction to Next Paint (INP) measures the latency between when a user interacts with a webpage and when the next paint occurs. It captures the responsiveness of web pages and users' experience by reflecting the time it takes for visible feedback to appear.

How Browser Rendering Affects INP

Browser rendering involves multiple steps, including parsing HTML, constructing the DOM tree, calculating styles, layout generation, and painting pixels on the screen. Any inefficiencies or delays in these processes can result in longer INP durations. Optimizing rendering paths is crucial for reducing these delays and ensuring a smoother user experience.

Optimizing Rendering Paths

Efficient CSS Management

Efficient CSS management is vital for improving rendering performance. Minimize CSS file sizes by removing unused CSS rules and compressing stylesheets. Use <link rel="preload" href="styles.css" as="style"> to preload critical CSS files and ensure they are available as soon as possible.

[Optimize CSS Delivery, 2022]

Minimize JavaScript Execution

JavaScript can block rendering; thus, it’s important to defer non-critical scripts or load them asynchronously using the defer and async attributes. This ensures that these scripts do not block the construction of the DOM.

[Defer Non-Critical JavaScript, 2023]

Use of Request Animation Frame (rAF)

For animations or visual updates, use the requestAnimationFrame (rAF) API to synchronize JavaScript execution with the browser’s paint cycle. This reduces unnecessary reflows and repaints, improving rendering efficiency.

[Using requestAnimationFrame, 2021]

Rendering Path Optimization

Reducing the critical rendering path involves inlining essential CSS and JavaScript directly into the HTML to minimize the time to first render. Additionally, implement resource hints like <link rel="preconnect"> to establish early connections.

[Understanding the Critical Rendering Path, 2023]

Improving Rendering Efficiency

Layer Management

Modern browsers use layers to manage rendering. Leveraging CSS properties like will-change can promote elements to their own layers, reducing composite work and increasing rendering efficiency.

[will-change, 2023]

Minimize Layout Thrashing

Layout thrashing occurs when scripts measure and modify the layout repeatedly. Batch DOM read and write operations together to avoid this issue, ensuring efficient rendering.

[Rendering Performance, 2018]

Optimized Image Loading

Use responsive images to serve appropriately sized images for different device types, reducing unnecessary rendering overhead. Additionally, employ modern formats like WebP to achieve better compression and faster loading times.

[Image Optimization, 2023]


Improving Interaction to Next Paint (INP) involves comprehensive optimization of the rendering paths. By managing CSS and JavaScript efficiently, leveraging the Request Animation Frame API, reducing the critical rendering path, and optimizing image loading, developers can enhance the responsiveness and visual feedback of web pages. Implementing these best practices will lead to better INP scores and an improved user experience.