PrestaShop Image Optimization: Alt Tags, Lazy Loading and Page Speed

Images are critical for e-commerce — customers need to see what they are buying. But images are also the biggest performance bottleneck for most PrestaShop stores. Product photos, category banners, and promotional graphics typically account for 50-70% of total page weight. Optimizing them is one of the fastest ways to improve both page speed and SEO.

Alt Tags: The SEO Foundation

Every image on your store should have a descriptive alt attribute. Alt tags serve three purposes:

• Accessibility: Screen readers use alt text to describe images to visually impaired users. This is not optional — it is a legal requirement in many jurisdictions.
• SEO: Google cannot "see" images the way humans do. Alt text tells search engines what an image contains, helping your products appear in Google Image search results.
• Fallback: When images fail to load (slow connections, broken links), alt text displays in place of the image.

Writing Effective Alt Tags

Good alt text is descriptive but concise:

• Good: alt="PrestaShop SEO sitemap builder module dashboard"
• Bad: alt="image1" or alt="" or alt="prestashop seo module best seo tool for prestashop seo optimization"

Describe what the image shows, naturally include relevant keywords, and keep it under 125 characters. For product images, include the product name and distinguishing feature: "Red leather wallet — front view with card slots visible".

With hundreds of products, writing individual alt tags for every image is time-consuming. Automated solutions that generate alt tags based on product names, categories, and attributes save hours of manual work while ensuring every image is properly tagged.

Lazy Loading: Load What Matters First

Lazy loading delays the loading of images that are not visible on the screen until the user scrolls to them. On a category page with 20 products, only the first 4-6 are visible without scrolling. Why load all 20 images upfront?

The benefits of lazy loading are substantial:

• Faster initial page load: The browser downloads fewer resources upfront, making the page interactive sooner.
• Lower bandwidth usage: Visitors who do not scroll to the bottom never download those images.
• Better Core Web Vitals: Largest Contentful Paint (LCP) improves because the browser focuses on above-the-fold content first.
• Reduced server load: Fewer simultaneous image requests mean better performance during traffic spikes.

Implementation Considerations

Modern browsers support native lazy loading via the loading="lazy" attribute, but for consistent cross-browser behavior and better control, a JavaScript-based solution is often preferred. Key considerations:

• Never lazy-load above-the-fold images — the first visible product images should load immediately.
• Use a placeholder (blurred thumbnail or solid color) while images load to prevent layout shift.
• Ensure the solution works with PrestaShop's product listing pages, search results, and category filters.

Image Compression and Format

Before worrying about alt tags and lazy loading, make sure your images are not unnecessarily large:

• Resize before uploading: A 4000x4000 pixel image displayed at 400x400 pixels wastes 99% of its data.
• Use WebP format: WebP images are 25-35% smaller than JPEG at equivalent quality. PrestaShop 8+ supports WebP generation.
• Compress aggressively: For product photos, JPEG quality of 80-85% is visually indistinguishable from 100% but significantly smaller.
• Use responsive images: Serve different sizes for mobile, tablet, and desktop instead of one large image for all devices.

Measuring the Impact

Use Google PageSpeed Insights and Core Web Vitals reports in Search Console to measure your improvement. Focus on:

• LCP (Largest Contentful Paint): Should be under 2.5 seconds. Image optimization directly affects this.
• CLS (Cumulative Layout Shift): Properly sized images with width/height attributes prevent layout jumps.
• Total page weight: Track this in your browser developer tools. A well-optimized product page should be under 1.5 MB.

Image optimization is one of those rare improvements that benefits everyone simultaneously: better SEO, faster user experience, lower hosting costs, and higher conversion rates.