How to Reduce LCP on Mobile for the Dawn Theme in Shopify: A Step-by-Step Guide

By Tony Ng.
June 20th, 2024

How to Reduce LCP on Mobile for the Dawn Theme in Shopify: A Step-by-Step Guide

Introduction

Reducing Largest Contentful Paint (LCP) on mobile devices is crucial for enhancing user experience and improving your Shopify store's performance, especially if you're using the Dawn theme. If you've been struggling to solve this issue despite optimizing images, this guide will walk you through the process to achieve a faster LCP. Let's dive into the steps and strategies to help you get your site to pass core web vitals with flying colors.

What is LCP and Why is It Important?

LCP stands for Largest Contentful Paint, a metric that measures the time it takes for the largest content element (usually an image or video) to appear on the viewport. A fast LCP is essential because:

Improved User Experience: Fast-loading pages keep visitors engaged, reducing bounce rates.
SEO Benefits: Google considers LCP as a ranking factor, so reducing it can improve your search engine ranking.
Conversion Rates: Faster load times often lead to higher conversion rates.

Common Causes of Poor LCP on Mobile

Unoptimized Images

Even if you’ve optimized your images, they could still be impacting LCP if not properly configured. Large file sizes, lack of responsive images, and incorrect formats can contribute to this problem.

Misconfigured Code

As you mentioned, your code lacks defer or async tags. This means that script files might be blocking the rendering of the largest contentful element.

Third-Party Scripts

External scripts like analytics, ads, and widgets can slow down your site. They often load before the main content, affecting LCP.

Theme Customizations

Customizing your Dawn theme incorrectly can lead to inefficient loading times. Older versions of the theme might also lack recent performance improvements.

Step-by-Step Guide to Reduce LCP on Mobile for Dawn Theme

1. Optimize and Implement Responsive Images

Use Next-Gen Image Formats

Using formats like WebP can significantly reduce file size without compromising quality.

Implement Responsive Images

Utilize the srcset attribute to serve different image sizes based on the device's viewport.

<img src="image.jpg" srcset="image-small.jpg 480w, image-large.jpg 1600w" sizes="(max-width: 600px) 480px, 1600px">

2. Defer Non-Essential JavaScript

Adding defer or async to your script tags can prevent JavaScript from blocking HTML rendering.

Defer Example:

<script defer src="script.js"></script>

Async Example:

<script async src="script.js"></script>

3. Minimize Third-Party Scripts

Audit your third-party scripts and remove any that are not essential. For necessary scripts, use asynchronous loading to lessen the impact on LCP.

4. Update Your Dawn Theme

Ensure that you are using the latest version of the Dawn theme. Theme developers often release updates that improve performance and resolve known issues.

5. Lazy Load Images

Lazy loading defers the loading of non-critical images until they are about to appear in the viewport.

<img loading="lazy" src="image.jpg" alt="Product Image">

6. Optimize CSS

Inline Critical CSS

Move the critical CSS used above the fold into the <head> to reduce render-blocking requests.

<style>
/* Inline your critical CSS here */
</style>

Minify CSS Files

Minifying CSS reduces its file size, allowing it to load faster.

7. Use CDN for Faster Delivery

Content Delivery Networks (CDNs) can significantly speed up the loading time by serving your resources from locations geographically closer to the user.

8. Enable HTTP/2

HTTP/2 allows multiple files to be downloaded simultaneously on one connection, reducing the load time.

9. Monitor and Iterate

Finally, monitoring your website’s performance using tools like Google PageSpeed Insights or Lighthouse can help you identify areas of improvement and ensure sustained performance.

FAQ Section

1. How Can I Tell if My Images are Affecting LCP?

You can use performance analysis tools to identify which elements are contributing to LCP. These tools will highlight images and other large elements that are slowing down your page.

2. Can I Use Both `defer` and `async` on the Same Script?

No, you should use either one or the other. defer ensures the script loads in order, while async loads them as soon as they're ready, which might not be in order.

Conclusion

Reducing LCP on mobile devices for the Dawn theme involves a multi-faceted approach. By optimizing images, deferring non-essential JavaScript, minimizing third-party scripts, updating your theme, and using performance monitoring tools, you can significantly improve your page speed. Follow this step-by-step guide to ensure a faster, more reliable browsing experience for your mobile users.

If you've tried these steps and still face issues, consulting with a professional might be the best course of action to diagnose and resolve specific problems.