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How to Diagnose and Fix Slow Loading Times on Your Site

How to Diagnose and Fix Slow Loading Times on Your Site

Having a slow website can negatively impact your business in many ways. Long load times frustrate users, increase bounce rates, and hurt your search engine rankings. Diagnosing and resolving performance issues should be a top priority for any business that relies on their website to engage with customers.

In this guide, we’ll walk through the major factors that influence page load speeds and provide actionable tips to speed up your site. Follow these best practices and you’ll see noticeable improvements in site performance.

Check Page Speed Insights

The first step is getting objective data on your current site speed. Google’s PageSpeed Insights tool analyzes your homepage and generates a report on both mobile and desktop performance.

PageSpeed grades on a 0-100 scale and highlights opportunities to improve page load times. Focus on implementing the “high priority” suggestions first, as these will likely provide the biggest bang for your buck.

For more comprehensive reports, tools like Pingdom and WebPageTest allow you to test page load times from different locations and analyze detailed waterfall charts. These provide insights into which elements on your page took the longest to load.

Optimize Images

Images often make up the majority of a webpage’s size. Optimizing your images can significantly reduce load times.

Start by compressing large images. Use a tool like ImageOptim to crunch images down to an efficient size. Make sure to compare file sizes before and after – you’ll be surprised how much smaller images can get with barely noticeable quality loss.

Next, focus on image dimensions. Scale down oversized images to the size that they’ll actually appear on page. Set specific width and height parameters on tags to prevent the browser from needing to rescale images.

Lazy loading offscreen images drastically cuts initial page weight. Images only load when scrolled into viewport. This technique defers the loading of below-the-fold images.

Finally, serve images in next-gen formats. WebP and AVIF files are 25-50% smaller than JPEGs without sacrificing quality. Use the tag to serve WebP/AVIF to supported browsers and gracefully fall back to JPEGs for non-supported browsers.

Minify CSS, HTML and JavaScript

Minification removes whitespace and shortens variable names to reduce file size. This speeds up page load times by decreasing the number of bytes sent over the network.

For HTML files, remove comments and use an minifier tool like HTML Minifier.

For CSS and JS files, build a minified production version using a module bundler like Webpack. Configure your bundler to minify code when generating builds for production.

You can further optimize CSS delivery by inlining critical CSS directly into the HTML document. This allows the page to load immediately without having to wait for external CSS files. Load the rest of the CSS asynchronously.

Efficiently Load JavaScript

JavaScript often blocks other page elements from loading. Make sure to load JS efficiently using best practices like:

  • Async loading for non-critical scripts
  • Defer loading for scripts that depend on earlier ones
  • Minimizing DOM manipulation scripts
  • Avoiding long-running JavaScript tasks on page load

Also pay attention to the number of JavaScript requests. Reduce HTTP requests by combining multiple scripts into one file using a bundler like webpack.

Use code splitting to break up large bundles into smaller pieces that can be loaded on demand. For example, load the main app code first, then asynchronously load other chunks to populate different sections and widgets on the page.

Optimize Web Font Loading

Web fonts can significantly increase page weight and lead to a flash of invisible text (FOIT).

Optimized font loading uses a font display strategy to set a brief invisible period, preventing FOIT. The CSS font-display property controls how custom fonts behave before loading.

Also lazy load non-critical icon fonts and web fonts for below-the-fold content. Utilize the CSS font-display property to load them asynchronously.

Preconnect to font CDNs like Google Fonts to initiate early DNS lookup and TLS negotiations.

Subsetting only loads font files needed for the pages you use, reducing file size. Generate custom font subsets using Font Squirrel.

Converting desktop fonts to webfont formats like WOFF and WOFF2 compresses file size and improves loading performance.

Minimize Redirects

Multiple server redirects can quickly add latency during page loads. Avoid unnecessary redirects wherever possible.

For essential redirects, consider supplementing with client-side JavaScript redirects to provide immediate feedback to the user.

Replace redirect chains with direct redirects to avoid multiple network round trips. Set up a redirect mapping if consolidating multiple old URLs.

Enable caching of redirect responses when possible via HTTP headers like Cache-Control. This avoids redirects requiring a full server roundtrip to check.

Reduce Server Response Time

Your server-side code impacts page load times. Slow database queries, unoptimized images, or other sluggish backend processes manifest directly in poor frontend performance.

Profile backend performance with tools like New Relic or Blackfire. Identify slow endpoints and optimize the codepath for these routes.

Caching improves backend response times by skipping expensive operations for repeat requests. Implement caching where possible, but ensure cache invalidation when data changes.

Lazy load API requests for non-critical data. Use frontend logic to defer API calls until truly needed.

Stream partial responses for long requests by sending data as it’s ready, rather than all at once when complete. This incremental loading prevents blocking.

Go serverless to auto-scale with usage spikes. Leverage AWS Lambda, Azure Functions, or Google Cloud Functions to run code in response to events.

Prioritize Content Visibility

While optimizations improve load times, users still suffer when forced to stare at a blank page.

Prioritize showing content as soon as possible, even if the full page hasn’t loaded. This content visibility provides a perceived performance boost.

Render the page shell with minimal HTML/CSS without waiting for other resources. Fill in content as asynchronously loaded resources complete.

Show placeholders such as skeleton screens to indicate content is on the way. Skeletons improve perceived load times.

Leverage service workers to cache and serve pages offline-first, then update in the background when online. This provides instant first visit loads.

Preload resource hints tell the browser to start fetching a resource with high priority as early as possible.

Code splitting chunks allows you to dynamically load just the JS required for above-the-fold content first. Load other chunks later.

Benchmark Real User Performance

Synthetic tests provide generalized speed data, but real user monitoring is crucial to understand true page load times in the wild.

Real user data gives you visibility into field performance on diverse devices, connections, locations.

Use Real User Monitoring (RUM) tools like Calibre, SpeedCurve, or Akamai mPulse to collect timing data directly from user browsers. Look for spikes or consistently slow geo regions.

Segment users to isolate poorly performing groups based on location, device type, browser etc. Address experience issues affecting portions of your audience.

Set performance budgets and configure alerts when averages exceed thresholds. Continuously monitor field performance using RUM to catch regressions.

Use session replays to replay specific user sessions suffering from slow loads. Diagnose the root cause by inspecting resource loading.

Test on Budget Devices and Networks

Conduct testing using cheap phones and slow network connections (e.g. 2G, 3G) to simulate real world conditions.

This helps avoid optimizing for your own modern device and fast WiFi network which does not reflect real user experiences. Test like your users do.

When developing locally, throttle network speeds and add artifical latency to better model typical users. Chrome DevTools provides options to simulate various network and CPU conditions.

For automated testing, run Lighthouse benchmarks across emulated mobile devices and networks. Catch performance regressions on underpowered devices.

Continuously Monitor and Improve

Page speed optimization is an ongoing process, not a one-time fix. Continuously monitor field performance and lighthouse scores to catch any regressions or new issues.

Setup automated performance testing as part of CI/CD pipelines. Block deploys for significant performance drops or Lighthouse score decreases.

Regularly re-evaluate page content and remove unnecessary bloat over time. Follow up on all optimization opportunities highlighted by speed testing tools.

As you make changes, measure their impact using real user monitoring data and lighthouse audits. Only keep modifications that improve real world speed.

By following the best practices outlined in this guide, you can significantly improve the loading experience for your site visitors. Faster websites lead to happier customers, increased conversions, and improved search visibility. Make page speed a priority today.

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