Product images are often the single largest contributor to page weight on ecommerce sites. After migrating from WooCommerce to Shopify, image handling changes significantly: Shopify's CDN automatically converts images to WebP and serves them via Shopify's global CDN. But the migration process itself can introduce problems — low-resolution images, missing alt text, and oversized uploads — that hurt both performance and SEO.

How Shopify handles images differently from WooCommerce

WooCommerce image handling

Images stored in wp-content/uploads/ on your hosting server
WordPress generates multiple size thumbnails (thumbnail, medium, large, full)
Delivery from your server (or via a CDN plugin like Cloudflare, BunnyCDN)
Format: typically JPEG and PNG as uploaded
WebP: available via plugins (Imagify, ShortPixel, Cloudflare Polish) but not automatic

Shopify image handling

Images stored on Shopify's infrastructure (Shopify CDN, powered by Fastly)
Automatic WebP conversion when browser supports it
Automatic responsive image serving via URL parameters: image.jpg?width=800
Global CDN delivery — no additional CDN plugin needed
Maximum file size: 20MB per image upload
Maximum dimensions: 5000×5000px

Image quality issues during migration

Images imported at reduced resolution

When k-sync imports product images from WooCommerce, it fetches images via the WooCommerce product API, which returns the full-size image URLs. However, some WooCommerce stores serve medium-size thumbnails in their API responses rather than full-size images. Check post-migration that product images are at least 1000×1000px for adequate zoom quality in Shopify's product gallery.

Images with compressed quality from old uploads

Images uploaded to WooCommerce years ago may have been compressed or resized when originally uploaded. Migrating these to Shopify does not improve their quality — they arrive at the same quality they were stored in WooCommerce. The migration is an opportunity to audit and replace low-quality product images.

Alt text not migrated

WooCommerce stores alt text at the WordPress Media Library level (the alt field on the attachment post). This is separate from the product, and many WooCommerce export tools don't include it. k-sync fetches alt text from the WooCommerce API where available (images[].alt field), but many WooCommerce stores have empty alt text even in WooCommerce.

Shopify CDN image URL parameters

Shopify's image CDN supports URL parameters for on-the-fly resizing. Understanding these helps with theme development and manual fixes post-migration:

// Original:
https://cdn.shopify.com/s/files/1/0000/0001/products/shirt.jpg

// Resize to 800px width (maintains aspect ratio):
https://cdn.shopify.com/s/files/1/0000/0001/products/shirt_800x.jpg

// Resize to exactly 800×600 (crops if needed):
https://cdn.shopify.com/s/files/1/0000/0001/products/shirt_800x600.jpg

// Or via URL parameter (in liquid):
{{ product.featured_image | image_url: width: 800 }}

In Shopify Liquid, always use image_url with a width parameter rather than serving the full-size original. This is the single biggest performance improvement available.

LCP (Largest Contentful Paint) after migration

LCP is typically dominated by the product hero image on product pages or the hero banner on the homepage. After migration, LCP regressions are common because:

The new theme may have a different, larger hero image
Images are being served at full resolution without width parameters
The loading="lazy" attribute may be incorrectly applied to above-the-fold images

The above-the-fold hero image should always have loading="eager" (or no loading attribute) and a fetchpriority="high" attribute to trigger early browser loading. Check your theme's product gallery and homepage hero image markup after migration.

Alt text strategy after migration

Every product image should have descriptive alt text for:

Accessibility (screen reader users)
Google Image Search visibility
SEO relevance signals

After WooCommerce migration, alt text can be updated in Shopify admin two ways:

Shopify admin: Products → [Product] → Images → hover over image → Edit alt text. Time-consuming for large catalogs.
Bulk via Shopify API: The productImageUpdate mutation accepts altText. A script can batch-update alt text from a CSV export.

A practical alt text formula for product images: "[Brand] [Product Name] — [Colour/Variant] [Key Descriptor]". Example: "Nike Air Max 90 — Triple Black men's running shoe".

Image file naming after migration

WooCommerce images often have poor file names: product-12345.jpg or img_0042.jpg. Shopify preserves the original file name when uploading. While Shopify's CDN URL doesn't show the file name in the same way as WordPress URLs, the image file name does appear in Google Image Search and can influence ranking.

Before migration, rename key product images to descriptive names where possible: nike-air-max-90-triple-black-side-view.jpg.

Post-migration image checklist

All product hero images are minimum 1000×1000px at the upload size
Above-the-fold images have fetchpriority="high" and no lazy loading
All below-the-fold images use loading="lazy"
Shopify Liquid uses image_url: width: N for all image output (not full-size)
Product alt text populated with descriptive keywords (not empty)
Homepage hero image LCP measured in Google PageSpeed Insights — target under 2.5s
No images exceeding 5000×5000px upload size
Variant images assigned to the correct variant (not just the first variant)
Image carousel / gallery working correctly on mobile after theme switch

Shopify image optimisation after migrating from WooCommerce (2026)