Improving Time-to-Interactive in React Apps with Server-Side Rendering

    Friday, May 31, 202410 min read109 views
    Improving Time-to-Interactive in React Apps with Server-Side Rendering

    Fast Time-to-Interactive is crucial for retaining user engagement and enhancing the overall user experience of web applications. In today's fast-paced digital world, users expect websites to load quickly and respond instantly to their interactions. Achieving fast Time-to-Interactive can be challenging, especially in complex single-page applications built with frameworks like React.

    In this blog post, we'll explore how Server-Side Rendering (SSR) can significantly improve Time-to-Interactive in React applications. SSR allows us to pre-render the initial HTML content on the rendering server side and send it to the client, reducing the time it takes for the page to become interactive. We will study deep into the concepts of Time-to-Interactive, SSR and provide practical guidance on implementing and optimizing SSR in React apps.

    Understanding Time-to-Interactive

    Time-to-Interactive (TTI) measures how long it takes for a fully rendered page of a web page to become fully interactive and responsive to user input after the initial page load. It is a critical performance metric that directly impacts user engagement, conversion rates, and search engine rankings.

    Several factors can contribute to slow TTI in React apps, including large JavaScript bundles, inefficient rendering processes, and excessive network requests. These issues are particularly in client-side rendering (CSR) where the browser must download and execute several JavaScript files before rendering the page content, resulting in delays in TTI.

    Introduction to Server-Side Rendering (SSR)

    Server-side rendering (SSR) is a technique that involves generating HTML content on the server and sending it to the client, where it can be displayed immediately. Unlike client-side rendering, which depends on JavaScript to render content in the browser, server-side rendering delivers pre-rendered HTML, significantly reducing the time it takes for the page to fully rendered HTML and become interactive.

    SSR offers several benefits, including improved perceived performance, better SEO optimization, and enhanced accessibility for users with slow or unreliable network connections. In React apps, SSR can be implemented using frameworks like Next.js or through custom server setups using libraries like Express.js.

    Implementing Server Side Rendering in React

    Implementing server-side rendering in a React app requires configuring the server to render React components on the fly and send the generated HTML to the client. With Next.js, setting up SSR is straightforward, as it abstracts away much of the complexity involved in server configuration and routing.

    Implement SSR with Next.js

    To implement SSR with Next.js, developers simply need to create a page that fetches data from the server and passes it to the component props. Next.js handles the server-side rendering process automatically, allowing developers to focus on building React components without worrying about React server-side rendering and setup.

    For example:
    1. Setting up the Project:

    First, we can create React app as a new project using a tool called Next.js. This tool helps us build React applications more easily.

    2. Creating Pages:

    In our project, we made a page called "Home". This page is like a section of a website where we want to show something. On our Home page, we want to display a greeting message.

    // This is our Home page
    import React from 'react';
    // This is a function that represents our Home page
    const Home = ({ data }) => {
      // Inside this function, we create what we want to show on our Home page
      return (
          <h1>Hello, SSR!</h1>
    // This function helps us get data before showing our page
    export async function getServerSideProps() {
      // We pretend to get some data from a special place
      const data = "Data fetched on server-side";
      // We give this data to our Home page to use
      return { props: { data } };
    // This makes our Home page available for other parts of our app to use
    export default Home;

    3. Running the Application:

    We start our project, and Next.js helps us run it on our computer. Then, we visit our project in a web browser.

    When we go to the Home page in our browser, we see the greeting message "Hello, SSR!" and some additional data, like "Data fetched on server-side". This extra data is fetched (retrieved) frequent server requests it from a special place before showing the page.


    • Pages and Routing: Each file we create inside a folder called "pages" becomes a different page on our website. So, our Home page is shown when we go to the main address of our website.

    • getServerSideProps Function: This function is like a helper that gets data for our page before showing it. It helps our page get ready with all the information it needs to show.

    • Component Rendering: Our page is made of a bunch of components (like building blocks) put together. We write a function to decide how these components should look and what data they should have. When someone visits our website, the server prepares everything in advance, including fetching data if needed, and sends it to their browser so they can see it quickly.

    Next.js makes it easy for us to build websites that load quickly and show the right information to people, thanks to features like Server-Side Rendering (SSR).

    Implement SSR with Express.js

    For custom SSR setups, developers can use libraries like Express.js to create a server that renders React components on incoming requests. This approach offers more flexibility but requires manual configuration of routing, data fetching, and server-side rendering logic.

    For example:

    1. Setting up the Project:

    First, create a new directory for your own project directory, and initialize a Node.js project.

    mkdir express-react-ssr
    cd express-react-ssr
    npm init -y
    npm install express react react-dom

    2. Creating the React Component:

    Create a new directory named src in your project root, and within it, create a file named App.js for your main React component.

    // src/App.js
    import React from 'react';
    const App = () => {
      return (
          <h1>Hello from React!</h1>
          <p>This content is rendered on the server-side with SSR.</p>
    export default App;

    3. Setting up the Express Server:

    Create a directory named server in your project root, and within it, create a file named index.js for your Express server.

    // server/index.js
    const express = require('express');
    const React = require('react');
    const ReactDOMServer = require('react-dom/server');
    const App = require('../src/App').default;
    const server = express();
    const PORT = process.env.PORT || 3000;
    server.get('/', (req, res) => {
      const app = ReactDOMServer.renderToString(<App />);
            <title>Express React SSR Example</title>
            <div id="root">${app}</div>
            <script src="/bundle.js"></script>
    server.listen(PORT, () => {
      console.log(`Server is running on port ${PORT}`);

    4. Creating a Build Script:

    Since we're not using tools like Webpack or Babel in this simple example, we need to create a build script to bundle our client-side JavaScript code.

    Create a script directory in your project root, and within it, create a . js file, named build.js.

    // scripts/build.js
    const fs = require('fs');
    const path = require('path');
    const { exec } = require('child_process');
    // Run Babel to transpile JSX and ES6 to ES5
    exec('npx babel src --out-dir dist', (error, stdout, stderr) => {
      if (error) {
        console.error(`Error: ${error.message}`);
      if (stderr) {
        console.error(`stderr: ${stderr}`);
      console.log(`Transpilation successful!\n${stdout}`);
      // Copy the bundled JavaScript file to the public directory
      fs.copyFileSync(path.resolve(__dirname, '../dist/App.js'), path.resolve(__dirname, '../public/bundle.js'));

    5. Running the Application:

    Now, let's create a build script that transpiles our React code using Babel and bundles it into a single JavaScript file.
    Finally, start the Express server:

    node server/index.js


    • React Component: We create a simple React component ( App) that renders some content.

    • Express Server: We set up an Express server that serves our React application. When a request is made to the root URL ( /), the server renders the React component to HTML using ReactDOMServer.renderToString() and sends it to the client.

    • Build Script: We create a build script that transpiles JSX and ES6 code to ES5 using Babel. The transpiled code is then bundled into a single JavaScript file ( bundle.js) and placed in the public directory, which the Express server serves to clients.

    This example demonstrates a basic setup for implementing SSR in a React application using Express.js. You can extend it further by adding more routes, optimizing the build process, and integrating with other libraries or APIs as needed.

    Optimizing SSR Performance

    Dynamic Imports and Lazy Loading

    Dynamic imports enable you to load JavaScript modules asynchronously, which can be particularly useful in SSR setups. By lazy loading non-essential components and resources, you can prioritize the initial rendering of critical content while deferring the loading of less important assets until they're needed. This approach helps minimize the initial payload size and improves TTI by reducing unnecessary resource loading.

    Optimizing Images

    Images often contribute significantly to page load times. When implementing SSR, consider optimizing image loading by using techniques such as lazy loading, responsive images, and image compression. Additionally, pre-rendering image placeholders on the server can improve perceived performance by providing visual feedback to users while images are loading.

    Prefetching Navigation

    In addition to prefetching data, consider prefetching navigation links to speed up subsequent page transitions. By prefetching linked pages during SSR or in response to user interactions, you can reduce the perceived latency between navigating to different sections of your application, further enhancing the overall user experience.

    Client-Side Hydration

    While SSR provides a fast initial rendering, client-side hydration ensures that the React components become fully interactive once the JavaScript bundle is loaded and executed in the browser. Optimizing hydration performance is critical for achieving fast TTI, especially in applications with complex client-side interactions. Techniques such as minimizing re-renders, optimizing event listeners, and avoiding unnecessary state updates can help improve hydration speed.

    Progressive Web App (PWA) Features

    Incorporating Progressive Web Apps features such as service workers, offline support, and app shell architecture can further enhance the performance and reliability of your SSR-enabled React application. PWAs leverage client-side caching and background processes to deliver seamless experiences, even in unreliable network conditions, ultimately improving TTI and user engagement.

    Content Delivery Network (CDN) Integration

    Integrating a CDN into your SSR setup can improve content delivery speeds by caching static assets closer to users geographically. By serving pre-rendered content and assets from edge locations, CDNs help reduce latency and improve TTI for users accessing your application from various regions worldwide.

    Optimized Server Infrastructure

    Ensure that your server infrastructure is optimized to handle SSR requests efficiently. Consider factors such as server response times, resource utilization, and scalability when configuring and provisioning server resources. Load balancing, auto-scaling, and caching strategies can help distribute server load and ensure consistent performance during peak traffic periods.

    A/B Testing and Performance Monitoring

    Conduct A/B testing to evaluate the impact of SSR optimizations on TTI and user engagement metrics. By comparing different SSR implementations and configurations, you can identify the most effective strategies for your application. Additionally, implement robust performance monitoring tools and practices to detect and address performance regressions proactively.

    By incorporating these advanced optimization strategies into your SSR-enabled React application, you can further enhance Time-to-Interactive, delivering fast and responsive user experiences that drive engagement and satisfaction.

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    Measuring and Monitoring TTI

    Real User Monitoring (RUM)

    Implementing RUM tools allows developers to gather performance data directly from users' browsers in real-time. By collecting metrics like TTI from actual user interactions, teams gain valuable insights into the end-user experience across different devices, browsers, and network conditions.

    Custom Metrics and Thresholds

    Define specific TTI thresholds tailored to your application's performance goals and user expectations. Custom metrics can help identify deviations from expected behavior and trigger alerts or notifications when TTI exceeds predefined limits, enabling rapid response to performance issues.

    Correlation with Business Metrics

    Link TTI measurements with key business metrics such as conversion rates, bounce rates, and user engagement metrics. By correlating TTI with business outcomes, teams can prioritize optimization efforts based on their impact on overall performance and user satisfaction.

    Performance Budgets

    Establish performance budgets that define acceptable limits for TTI and other performance metrics. By setting clear targets for TTI and regularly monitoring performance against these budgets, teams can ensure that new features and updates maintain or improve overall performance without introducing regressions.

    Error Monitoring and Diagnostics

    Integrate error monitoring tools with performance monitoring solutions to correlate TTI metrics with error rates and diagnostic information. By identifying correlations between performance issues and errors, teams can address underlying issues more effectively and minimize their impact on user experience.

    Long-Term Trend Analysis

    Analyze TTI trends over time to identify patterns and seasonality in performance data. Long-term trend analysis helps teams anticipate performance fluctuations, plan for scalability, and prioritize optimization efforts based on historical data insights.

    Cross-Browser and Device Testing

    Perform TTI measurements across different browsers, devices, and network conditions to ensure consistent performance across diverse user environments. By conducting comprehensive cross-browser and device testing, teams can identify platform-specific performance issues and optimize accordingly.

    Integration with CI/CD Pipelines

    Integrate TTI monitoring into continuous integration and continuous deployment (CI/CD) pipelines to automate performance testing and validation processes. By incorporating TTI measurements into automated testing workflows, teams can detect performance regressions early in the development lifecycle and prevent them from reaching production environments.

    Collaborative Performance Reviews

    Conduct regular performance reviews with cross-functional teams to discuss TTI metrics, identify optimization opportunities, and prioritize performance-related initiatives. Collaborative performance reviews foster a culture of performance optimization and ensure alignment between development, QA, and operations teams.

    User Feedback and Surveys

    Gather feedback from users through surveys, feedback forms, or user interviews to understand their perceptions of application performance, including TTI. User feedback provides qualitative insights into the impact of performance optimizations on user satisfaction and helps prioritize improvements based on user needs and preferences.

    Case Studies and Real-World Examples

    Several popular websites and web applications have adopted SSR to improve TTI and deliver fast, engaging user experiences.

    Here is an in-detail example of server-side rendering adopted by enterprises:


    Airbnb is a popular platform for booking accommodations worldwide. They implemented Server-Side Rendering (SSR) using Next.js, a framework for React applications, to enhance their website's performance. By rendering pages on the server before sending them to users' browsers, they reduced the Time-to-Interactive (TTI) rendering web pages by 50%.

    Imagine you're planning a vacation and browsing Airbnb's website. With SSR, the pages load faster because much of the rendering work is done on Airbnb's servers before the content is sent to your browser. This means you can start searching for accommodations and exploring listings without waiting for the entire webpage to load. The faster TTI leads to higher user engagement, as people can quickly find what they're looking for and make bookings more efficiently.


    Netflix, the world's leading streaming service, also adopted SSR to improve their website's performance and user experience. By pre-rendering critical content on the server, they optimized TTI and enhanced SEO (Search Engine Optimization). This means that when you visit Netflix's website, important information like movie titles, descriptions, and images are already loaded, allowing you to start browsing instantly.

    Moreover, SSR improves SEO by ensuring that search engines can easily crawl and index content. When search engines like Google can quickly find and understand Netflix's web pages, they're more likely to show them in search results. This increased visibility leads to more organic traffic, as people searching for movies and TV shows are more likely to discover and visit Netflix's website.

    In both cases, Airbnb and Netflix leveraged SSR to deliver fast, engaging user experiences and achieve business objectives such as higher user engagement, conversion rates, and organic traffic. By optimizing TTI through SSR, these companies enhanced the performance and accessibility of their websites, ultimately improving the overall satisfaction of their users.

    Best Practices and Recommendations

    Based on our exploration of SSR and TTI optimization, here are some best practices and recommendations for developers:

    • Start by identifying critical paths and optimizing components that contribute most to TTI.

    • Leverage code splitting, data prefetching, and caching to minimize SSR overhead and improve performance.

    • Monitor TTI regularly using performance tools and establish benchmarks to track progress over time.

    • Consider the trade-offs between SSR and client-side rendering based on the specific requirements of your application.

    • Experiment with different SSR implementations and optimization strategies to find the best approach for your project.


    Server-side rendering (SSR) offers a powerful solution for improving Time-to-Interactive (TTI) in React applications. By pre-rendering content on both the client and server, SSR reduces the load on client-side rendering, resulting in faster page rendering and interaction.

    SSR alongside optimization techniques like code splitting and caching enhances performance and user experience. Continuous monitoring of TTI using tools like Lighthouse ensures ongoing optimization efforts. With SSR, developers can deliver fast, responsive web experiences that meet user expectations and drive engagement.

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