Progressive web apps (PWAs) provide an app-like experience on the web that rivals native mobile apps stated Bahaa Al Zubaidi. But if your PWA is slow to load, users may abandon it before ever seeing what it can do. Fortunately, many performance optimization techniques can help you boost load times and create the snappy experience users expect.
Minify Code
Minification removes unnecessary characters like whitespace, comments, and indentation from HTML, CSS, and JavaScript files. This results in smaller file sizes that load faster.
Enable minification in your build process using tools like Webpack. Manually minify code before deploying to production. Regularly audit minified files as new changes are introduced. Every byte reduced is an optimization.
Enable Code Splitting
Instead of downloading one large JavaScript bundle, split code into smaller chunks that can be lazily loaded as needed. This technique is called code splitting.
For example, split above-the-fold content that displays immediately from other functionality. Download only what’s necessary for the initial view. Lazy load other features as the user navigates.
Frameworks like React and Vue make code splitting easy to implement. The granularity of chunks can be configured, balancing download size with requests.
Use Tree Shaking
Tree shaking removes unused JavaScript code during the build process, reducing bundle size. It statically analyzes dependencies between modules to discard unused exports. This works well with code splitting.
For example, if component A exports utils X and Y but only Y is imported in component B, X can be safely shaken out. This removes dead code that would otherwise be bundled.
Compress Images
Images often account for most of a web page’s downloaded bytes. Compressing images like JPEGs and PNGs saves bandwidth and improves load speed.
Use tools like ImageOptim or Squoosh to crunch images. Enable compression in the build pipeline. Set maximum sizes for images. Also, convert large images to newer formats like WebP when possible.
Enable Compression
Gzip or Brotli compression for text content reduces file size and speeds up transfers. Compression is handled automatically by most servers.
Verify headers are properly configured on the server. Test compression using online tools. Compression ratios of 2:1 or better are common for HTML, CSS, and JS. Savings add up across all resources and requests.
Precache Key Routes
Precaching allows key pages like the home page to load instantly on repeat visits. During the service worker install phase, precache necessary assets in the cache. Resources are then available offline.
Precaching entire page views avoids roundtrips. But be selective, as cache storage is limited. Prioritize routes users visit most often for maximum benefit.
Lazy Load Offscreen Images
Defer loading of offscreen images that are below the fold until the user scrolls down. This prevents wasting bandwidth on images that aren’t seen.
For example, add the loading=”lazy” attribute to img tags. Or use libraries like Lazysizes. Fade in images as they load to create a smooth effect. Don’t lazy load above-the-fold images for immediate visibility.
Use Next-Gen Image Formats
Older image formats like JPEG 2000, GIF, and PNG are much larger in file size than newer options like WebP and AVIF. Leverage newer formats supported on most modern browsers for dramatic bandwidth savings.
For cross-browser support, use PNG or JPEG as a fallback. Image CDNs can handle serving optimized formats to supported browsers automatically. With ample savings per image, this quickly multiplies across a site.
Optimizing performance should be an ongoing process. Measure, optimize, repeat. As users wait less, engagement and conversion rates will rise. By incrementally employing techniques like the ones outlined here, your PWA will delight users with its snappy responsiveness.
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