Sidekick: Optimize Checkout Page Speed

Help me optimize the speed of my Shopify checkout page:

Store name: [YOUR STORE NAME]
Current checkout load time: [SECONDS OR UNKNOWN]
Number of third-party scripts: [COUNT OR UNKNOWN]
Checkout apps installed: [LIST ANY APPS AFFECTING CHECKOUT]

Optimize checkout page speed:


  
    Baseline measurement - Test the current checkout page load time using Google PageSpeed Insights, WebPageTest, and Lighthouse. Record the Time to First Byte (TTFB), Largest Contentful Paint (LCP), and Total Blocking Time (TBT) as baseline metrics.
  
  
    Script audit - Identify all third-party scripts loading on the checkout page. List each script, its source, its size, and its load time impact. Remove or defer any scripts that are not essential for checkout functionality: analytics scripts should load asynchronously, and marketing pixels should use lightweight implementations.
  
  
    Image optimization - Ensure all images on the checkout page (logo, trust badges, product thumbnails) are properly compressed and served in WebP format. Set explicit width and height attributes to prevent layout shifts. Use appropriately sized images rather than scaling large images down with CSS.
  
  
    Font optimization - Limit custom fonts on the checkout page to one family with a maximum of two weights. Use font-display: swap to prevent invisible text during font loading. Consider using system fonts for checkout to eliminate font loading entirely.
  
  
    CSS cleanup - Remove any unused CSS rules from the checkout stylesheet. Inline critical CSS needed for above-the-fold content and defer loading of non-critical styles.
  
  
    App impact assessment - Test checkout speed with each checkout app disabled one at a time to identify any apps that significantly slow down the page. Replace slow apps with lighter alternatives or remove them if the speed cost outweighs their benefit.
  
  
    Caching and CDN - Verify that static checkout assets (images, fonts, CSS) are being served from Shopify CDN with proper cache headers. Check that browser caching is working for returning customers.
  
  
    Monitoring - Set up ongoing speed monitoring using Google Analytics Web Vitals or a real user monitoring (RUM) tool. Create alerts if checkout load time exceeds [TARGET SECONDS] seconds.
  
  
    Target performance - Aim for a checkout page that loads in under 2 seconds on desktop and under 3 seconds on mobile on a standard 4G connection. Prioritize LCP and TBT improvements as they have the highest impact on conversion.
  


Provide an action plan ordered by expected impact, starting with the highest-impact optimizations.