Vibe coding a store speed audit tool — and finding 13MB of wasted images on one page
Loading speed quietly kills conversion, and most stores fix the wrong thing. I vibe-coded a tool that found 13MB of trimmable images on one page.
🧪 A GemLabs lab. This is a build journal — a weekend experiment using AI coding agents like Claude Code, written up so you can copy the pattern. You don’t need to be technical to read it. The takeaway isn’t the tool. It’s that you can describe a workflow in plain English and have an agent build it for you. Steal it.
Here’s a number that should bother every store owner: on one Shopify product page I tested, 13 MB of images could be removed without changing a single pixel a shopper sees. Not “compressed a little.” Removed. The page was shipping 13.7 MB of images; the same images, sized to what they actually display at and saved as WebP, came to 720 KB. That’s 95% lighter.
That page isn’t unusual. It’s normal. Most stores I look at are carrying this exact weight, and the owner has no idea — because the store looks fine on their fast office wifi and their newish phone. The customer on 4G in a tier-2 city is the one paying for it, in seconds they don’t wait around for.
GemPages’ own help center puts the cost plainly: once a page takes longer than 3 seconds, bounce rate jumps ~32%; at 5 seconds it’s ~90%. Slow stores are estimated to leak around $1.6 billion a year in lost sales across ecommerce. Speed isn’t a “nice to have” — it’s a conversion line item.
So I spent an evening vibe coding a tool that takes a URL and shows you exactly which images are bloated, by how much, and hands you the optimized files to download. Below: why most speed advice misses the real culprit, the 13 MB teardown, and a walkthrough you can actually follow so you can build (or just use) this yourself — no coding background required.
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