A buyer who has already added an item to their cart is the closest thing to a guaranteed sale you’ll ever get — and the slowest, heaviest images on your store are usually sitting right in front of them.
Most Shopify speed advice treats every page the same: shrink images, defer what’s off-screen, chase a better PageSpeed score. But a slow blog post costs you a bounce. A slow cart drawer, cart page, or checkout step costs you a sale that was already halfway closed — and most speed audits never look there.
Plug In Speed finds and compresses the oversized images actually loading on your storefront — including the ones sitting in your cart drawer and upsell blocks — without you digging through theme code to find them.
Which guide is this? For the full explainer on lazy loading — what it is, what Shopify 2.0 already handles natively, where the gaps are — read our lazy loading guide. This post goes narrower: specifically the images sitting between “add to cart” and “order confirmed.”
Why images near checkout cost more than images anywhere else
A visitor browsing your collection page is patient — comparing, scrolling, killing time. A visitor sitting in your cart or checkout has already decided to buy; they’re just waiting for the page to get out of their way. That shift in intent changes the cost of every extra second.
It also changes the cost of friction. On a browsing page, a slow-loading image might cost a few extra seconds of scroll. In checkout, a slow trust badge or a cart drawer that jumps around while thumbnails pop in can read as something being wrong — and shoppers already holding their card out are quick to bail rather than troubleshoot.
Where the weight actually comes from on Shopify
Most merchants assume checkout is lightweight because it doesn’t look image-heavy. In practice, four places quietly load more image data than they need to:
- Cart drawer thumbnails. Many themes pull the same large image file used on the product page into the cart drawer, then shrink it with CSS instead of serving a properly sized version. The browser still downloads the full-size file.
- Upsell and cross-sell carousels. “You might also like” blocks on the cart or checkout page often load 4–8 product images at once, sometimes before the shopper scrolls anywhere near them.
- Trust badges and payment icons. Small in dimension, but frequently served as unoptimized PNGs — adding avoidable weight for images that carry no product information.
- Oversized product images carried into checkout. Shopify pulls a product’s featured image into the order summary automatically. If that source image was never optimized, checkout inherits the same oversized file.
Step-by-step fixes
1. Audit what’s actually loading
Open your cart drawer and checkout in an incognito tab, run a waterfall check (Chrome DevTools’ Network tab, filtered to “Img”), and note file sizes over 100KB.
2. Resize cart and upsell thumbnails at the source
Don’t rely on CSS to shrink a 2000px photo to a 60px thumbnail — the browser still downloads the full file.
3. Convert to modern formats
WebP files typically run 25–35% smaller than the equivalent JPEG at the same visual quality.
4. Compress trust badges once, then reuse them
These are static assets that rarely change — optimize once and they stay optimized every session.
5. Cap carousel image counts and lazy-load below the fold
If an upsell block shows six products, only the first two or three need to load immediately.
6. Let an app handle ongoing compression
New product photos get added constantly — Plug In Speed compresses images across your storefront on an ongoing basis so this doesn’t become a recurring manual task.
How to verify you actually fixed it
- Re-run the waterfall check on your cart and checkout screens and confirm the total image payload dropped.
- Check Shopify’s built-in Web Performance report (Settings > Web Performance) for changes over the following 1–2 weeks.
- Watch your cart-to-checkout and checkout-completion rates in Shopify Analytics for the following two to four weeks — this is the metric that actually matters.
- Spot-check on a throttled mobile connection, not just office Wi-Fi.
General mobile/ecommerce speed research points the same direction, even though none of it is checkout-specific: a Google-commissioned study run by Deloitte Digital found a 0.1-second improvement in mobile page speed increased retail conversion rates by 8.4% and consumer spending by 9.2%. Portent’s analysis of ecommerce page performance found conversion rate drops from 3.05% at a 1-second load time to 0.67% at 4 seconds.
Think with Google — The Need for Mobile Speed
Frequently asked questions
Does image weight in the cart drawer actually slow down checkout, or just the cart page?
Both, if your theme reuses the same image file. Many themes load one large product image and reuse it everywhere — product page, cart drawer, and order summary in checkout — so an oversized file on the product page carries its weight all the way through.
Will Shopify’s native lazy loading fix this for me automatically?
Partially. Shopify 2.0 themes lazy-load many below-the-fold images by default, but cart drawers, upsell carousels, and checkout order summaries often load outside that default behavior because they’re injected dynamically. See our lazy loading guide for what’s covered natively.
Should I remove upsell image carousels from checkout entirely to speed things up?
Not necessarily — upsells are a legitimate revenue tool. The fix is resizing and lazy-loading the images inside them, not removing the carousel.
How do I know if my checkout images are actually oversized?
Open DevTools’ Network tab, filter to images, and load your cart and checkout screens. Any single image file over roughly 100KB on a checkout screen is a candidate for resizing.
Does trust badge and payment icon weight really matter compared to product photos?
Individually, one badge is small. But checkout pages often stack 4–6 of them, and if none were compressed on upload, that adds up to real weight on the one screen where every kilobyte is working against you.
Fixing checkout speed isn’t about chasing a better score — it’s about making sure the shopper who already decided to buy doesn’t lose momentum in the last thirty seconds.
Stop losing sales to slow checkout images
Plug In Speed finds and compresses the images actually loading in your cart drawer, upsells, and checkout — not just your product pages.
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