Progressive web apps (PWAs) running on any operating system are like makeshift houses that aren't rooted to the foundation. PWAs exist to bridge the gap between web pages and native applications. Built with standard web technologies of HTML, JavaScript, and CSS, PWAs are improvised web pages that masquerade as apps. They are installable and function just the same —without high development costs, heavy codebases, and app store listings. PWSs provide deeper access to device APIs and unfettered access to the underlying hardware. Filling the sweet spot between native apps and webpages, PWAs enable a fast fix for a quick need without the hassle of installing an application.
. This solution article explores the key ingredients of PWAs, their functioning, and ways to use ManageEngine Site24x7's website monitoring capabilities to run them efficiently, to deliver the best load time and performance.
Challenges of PWA performance on diverse devices
Despite its many benefits, ensuring consistent performance of PWAs across diverse devices, networks, and regions is a challenge. With optimization techniques such as intelligent caching and lazy loading backed with comprehensive performance monitoring, organizations running PWAs can ensure optimal user experiences across devices. We can classify the top challenges :
- Network Conditions: Fluctuations in bandwidth and latency impact load times and responsiveness.
- User Behavior: Unpredictable usage patterns, such as background app activity or privacy settings, can degrade performance.
- Hardware Variability: Differences in processing power, RAM, and GPU capabilities affect JavaScript parsing and rendering speeds. PWAs must deliver seamless experiences across a wide range of devices, from high-end smartphones on 5G to low-end tablets on unstable WiFi.
- Browser Differences: Variations in browser engines influence PWA performance.
The above factors create performance bottlenecks that require robust optimization and monitoring strategies to ensure consistent Service Level Agreements (SLAs) across ISPs and regions.
Techniques for caching and lazy loading
To optimize PWA performance, implement the following strategies:
Caching strategy:
- Adopt a cache-first approach using the Cache Storage API during the service worker's fetch event. Serve static assets (CSS, icons, fonts) from cache and fall back to network requests for dynamic content (e.g., user data, real-time feeds).
- Use stale-while-revalidate for high-frequency content like social media feeds to serve cached data instantly while updating in the background.
- Implement fallback mechanisms to serve cached content when network requests fail due to timeouts or offline conditions.
Lazy loading:
- Apply lazy loading for images below the viewport using the loading="lazy" attribute or Intersection Observer API to trigger loads when elements become visible.
- Use code splitting to dynamically import non-essential JavaScript modules only when needed, reducing initial load times.
- Render critical CSS inline in the HTML head and load non-critical CSS asynchronously.
- For fonts, display system fonts initially, switching to custom fonts once loaded to avoid delays.
These techniques minimize load times and enhance user experience, especially on low-end devices or weak networks.
Testing PWAs across device types
Testing PWAs across diverse devices is critical to identifying performance bottlenecks. Key considerations include:
- Real device testing: Simulate low-end hardware (e.g., devices with <2GB RAM) to uncover JavaScript parsing issues or rendering delays.
- Browser variability: Test across multiple browsers (Chrome, Firefox, Safari) to ensure compatibility and performance consistency.
- Network simulation: Replicate real-world network conditions (e.g., 3G, 4G, unstable WiFi) to assess performance under varying bandwidths.
Site24x7's synthetic monitoring supports testing across 130+ global locations, simulating various devices, browsers, and network conditions to catch issues early.
Monitoring load time metrics
Monitoring load time metrics is essential for benchmarking PWA performance. Focus on Core Web Vitals (CWV), which include:
- Largest Contentful Paint (LCP): Measures the time to render the largest visible content element, indicating perceived load speed.
- Interaction to Next Paint (INP): Assesses the responsiveness of the website by measuring the time taken from user interaction to the next visual update.
- Cumulative Layout Shift (CLS): Quantifies visual stability by tracking unexpected layout shifts during page load.
Site24x7's Real User Monitoring (RUM) captures CWV data from actual user sessions, segmenting performance by device type, OS, region, and ISP. This helps identify specific performance issues, such as slow LCP on low-end devices or high CLS due to unoptimized layouts.
How Site24x7 helps in improving PWA performance
First, Site24x7 calculates CWV by collecting performance data from real user sessions and synthetic tests. It tracks LCP, INP, and CLS across devices, browsers, and regions, providing actionable insights to optimize PWA performance. For example, a high LCP may indicate unoptimized images or heavy JavaScript bundles, while a high INP could point to main-thread blocking. Site24x7's dashboards highlight these metrics, enabling IT teams to prioritize fixes and improve user experience.
Using real device profiles in synthetic monitoring to simulate low-end performance
Site24x7's synthetic monitoring uses real device profiles to simulate low-end hardware and network conditions. Automated scripts run across 130+ locations, mimicking user interactions on various devices and browsers. Synthetic monitoring is essential to spot performance issues like slow rendering on low-RAM devices or high latency in specific regions, allowing teams to optimize PWAs for diverse scenarios.
Case Study: learning platform
Zylker Learn, an e-learning platform serving 30,000 users across 15 countries, faced performance issues with its PWA on mobile devices. During peak evening hours, course completion rates dropped due to 10-second load times on low-end Android devices. Using Site24x7's tools, the team:
- Conducted synthetic monitoring to simulate low-end smartphone environments, identifying bottlenecks like large video thumbnails, unoptimized JavaScript, and heavy custom fonts.
- Leveraged RUM data to confirm that devices with <2GB RAM experienced the worst performance.
- Implemented optimizations: lazy loading for images, code splitting for JavaScript, pre-loading critical course materials, and a minimalist design approach.
Results:
- Average load time dropped to under 3 seconds, even on low-end devices.
- Course completion rates surged, particularly among mobile users.
- Core Web Vitals scores improved too, reflecting better performance consistency.
Best Practices to optimize PWAs:
- Use HTTPS: Ensure secure data transit to support service workers and maintain user trust.
- Test rigorously: Validate performance on real devices, not just emulators, to uncover hardware-specific bottlenecks.
- Optimize code: Use CSS properties such as transform and opacity for animations to leverage GPU acceleration and reduce main-thread blocking.
- Adopt minimalism: Offload heavy tasks to web workers and prioritize lightweight designs to improve responsiveness.
- Monitor continuously: Use Site24x7 to track CWV, synthetic tests, and RUM data to maintain SLAs across ISPs and regions.
Sign-up for Site24x7 today to start optimizing your PWAs
Delivering fast, reliable PWAs requires overcoming real-world limitations such as device diversity and network variability. ManageEngine Site24x7 provides end-to-end monitoring with synthetic testing, RUM, and CWV tracking to ensure your PWAs perform like native apps— or better. Visit the Site24x7 Website Monitoring page to explore tools for optimizing PWA performance across all devices and user scenarios.