Boosting Blazor PWA Performance: 5 Proven Techniques 🚀

 

Blazor Progressive Web Apps (PWAs) offer the perfect combination of native-like functionality and cross-platform accessibility. However, as your application grows, ensuring optimal performance becomes critical. Slow-loading apps or unresponsive features can drive users away, especially in today’s fast-paced, mobile-first world.

In this post, we’ll cover 5 proven techniques to boost the performance of your Blazor PWA. By implementing these tips, you can create a fast, responsive, and efficient application that keeps users engaged.

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1. Implement Lazy Loading for Components and Data

Lazy loading defers the loading of resources until they are needed, reducing the initial load time of your Blazor PWA. This is particularly useful for components, data, and images that users may not interact with immediately.

Lazy Loading Components

Blazor allows you to conditionally render components, ensuring they are only loaded when required:

@if (isComponentVisible)
{
    <MyComponent />
}
<button @onclick="ShowComponent">Load Component</button>

@code {
    private bool isComponentVisible = false;

    private void ShowComponent()
    {
        isComponentVisible = true;
    }
}

Lazy Loading Images

Use the loading="lazy" attribute in HTML to delay the loading of images until they appear in the viewport:

<img src="images/large-image.jpg" alt="Lazy Loaded Image" loading="lazy" />

Lazy Load Assemblies

Blazor WebAssembly supports lazy loading of assemblies. This is useful for modular apps with features that users may not access frequently:

await JSRuntime.InvokeVoidAsync("import", "./path-to-module.js");

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2. Leverage Ahead-of-Time (AOT) Compilation

By default, Blazor WebAssembly uses an interpreter to run .NET code in the browser. While this works well for most scenarios, enabling Ahead-of-Time (AOT) compilation can significantly improve runtime performance by compiling your .NET code directly to WebAssembly.

Enable AOT Compilation

Add the following property to your .csproj file:

<PropertyGroup>
    <RunAOTCompilation>true</RunAOTCompilation>
</PropertyGroup>

Build your application in release mode:

dotnet publish --configuration Release

AOT compilation reduces the size of the interpreted runtime, improving startup times and execution speed. However, it may increase build times, so it’s best used for production builds.

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3. Use Virtualized Components for Large Data Sets

Rendering large amounts of data can degrade performance and lead to sluggish UIs. Blazor’s Virtualize component provides a solution by only rendering the visible portion of a list, loading additional items as the user scrolls.

Example: Virtualizing a Data Table

<Virtualize Items="data" Context="item">
    <div>@item.Name</div>
</Virtualize>

@code {
    private List<MyData> data = Enumerable.Range(1, 1000).Select(i => new MyData { Name = $"Item {i}" }).ToList();

    private class MyData
    {
        public string Name { get; set; }
    }
}

This approach reduces memory usage and improves rendering speed, especially for applications with thousands of records.

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4. Optimize Static Assets

Optimizing your app’s static assets (CSS, JavaScript, images) can greatly improve load times and overall responsiveness.

Minify and Bundle CSS/JavaScript

Use tools like Webpack or Gulp to minify and bundle your CSS and JavaScript files. This reduces their size and the number of HTTP requests:

npm install -g uglify-js
uglifyjs main.js -o main.min.js

Serve Optimized Images

• Convert images to modern formats like WebP, which offers better compression.
• Resize images to appropriate dimensions before uploading them to reduce unnecessary data transfer.

Use a Content Delivery Network (CDN)

Host static assets on a CDN to reduce latency and improve download speeds by serving resources from servers closer to users.

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5. Optimize Caching with Service Workers

Blazor PWAs use service workers to enable offline capabilities and cache assets. Optimizing the caching strategy can improve performance by reducing unnecessary network requests.

Pre-Cache Static Resources

Update the service worker (wwwroot/service-worker.js) to cache critical files during the installation phase:

self.addEventListener('install', event => {
    event.waitUntil(
        caches.open('app-cache-v1').then(cache => {
            return cache.addAll([
                '/',
                '/index.html',
                '/css/app.css',
                '/_framework/blazor.webassembly.js'
            ]);
        })
    );
});

Implement Cache-First Strategy

For assets that don’t change often (e.g., images, CSS), use a cache-first strategy to serve them faster:

self.addEventListener('fetch', event => {
    event.respondWith(
        caches.match(event.request).then(response => {
            return response || fetch(event.request);
        })
    );
});

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Bonus Tips

• Reduce JavaScript Interop: While JavaScript interop is powerful, excessive usage can slow down your app. Optimize interop calls by batching them when possible.
• Enable HTTP/2 or HTTP/3: Use a server that supports HTTP/2 or HTTP/3 for faster loading of multiple resources.
• Profile and Test Regularly: Use tools like Chrome DevTools, Lighthouse, and Azure Application Insights to identify performance bottlenecks and optimize accordingly.

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Conclusion

Optimizing the performance of your Blazor PWA ensures a seamless, responsive experience for users while maintaining scalability for future growth. By implementing lazy loading, AOT compilation, virtualized components, and effective caching strategies, you can deliver a fast and efficient application that stands out in today’s competitive web landscape.

Ready to build lightning-fast Blazor PWAs? Check out my book, Building Progressive Web Apps with Blazor, for more in-depth techniques, real-world examples, and expert insights.

Start optimizing today, and give your users the performance they deserve! 🚀