How to Add Lazy Load and Default Thumbnail Images in Blogger (JetTheme Guide)

How to Add a Lazy Load Placeholder Image to JetTheme Blogger Template

Adding lazy load and default thumbnail support to your Blogger website not only boosts performance but also ensures a clean, professional design. This tutorial only for JetTheme

✨ Why Use Lazy Load + Default Image?

Faster page loading

Fallback for missing or broken images

Better SEO and UX

✅ Step 1: Choose a Default Image

Upload an image to a hosting service (e.g. GitHub, Google Drive) and copy its direct link. Example:

https://cdn.jsdelivr.net/gh/TheRealAnwarul/Photos@main/Face-The-Village.png

✅ Step 2: Update Homepage Thumbnails (JetArchive)

Go to: Find This

<img expr:alt='data:post.title' expr:class='data:post.featuredImage.isYoutube ?  &quot;object-cover lazyload&quot; : &quot;lazyload&quot;' expr:data-src='data:post.featuredImage.isYoutube ? data:post.thumbnailUrl : data:post.featuredImage' src='data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw=='/>

Replace the blocks with:

<img class='lazy-thumb' 
     expr:alt='data:post.title'
     src='https://cdn.jsdelivr.net/gh/TheRealAnwarul/Photos@main/Default-thumbnail.png'
     expr:data-src='data:post.featuredImage'
     onerror="this.onerror=null;this.src='https://cdn.jsdelivr.net/gh/TheRealAnwarul/Photos@main/Default-thumbnail.png';"/>

Changes Yellow mark Link and add Your Link

✅ Step 4: JavaScript for Lazy Loading

Paste this before </body>:

<script>
document.addEventListener("DOMContentLoaded", function () {
  const lazyThumbs = document.querySelectorAll("img.lazy-thumb");
  lazyThumbs.forEach(img => {
    const originalSrc = img.getAttribute("data-src");
    if (originalSrc) {
      const temp = new Image();
      temp.onload = () => { img.src = originalSrc; };
      temp.onerror = () => { img.src = img.src; };
      temp.src = originalSrc;
    }
  });
});
</script>

✅ Step 4: Add Optional CSS

<style>
img.lazy-thumb {
  transition: opacity 0.4s ease;
  opacity: 0.85;
  object-fit: cover;
}
</style>

🚀 Final Result

Faster page loads

Placeholder default image

Real image loads after site is ready

Perfect for SEO + mobile

Author: Mr Anwarul IslamSource: www.mranwarulislam.com