PrestaShop slowness gets blamed on hosting and themes. The benchmark points at something smaller and more fixable: the format your product images are served in.
When a PrestaShop store loads slowly, the suspects are usually the expensive ones: cheap hosting, a heavy theme, too many modules. Any of those can be the problem. But across the PrestaShop stores we audited, the single most common issue we found was none of them. It was the images, and specifically the format they were served in.
Images are the heaviest thing on the page
On an ecommerce store, the images are almost always the largest things a browser has to download. A product page is mostly photographs: the gallery, the thumbnails, the related products, the lifestyle shots. Text and code are light by comparison. So when the images are heavier than they need to be, the whole store is, and it shows most on exactly the pages where shoppers spend their time deciding whether to buy.
The image-format upgrade most PrestaShop stores miss
PrestaShop can serve images in modern formats like WebP, which are often significantly smaller than the same photo saved as a JPEG or PNG, at comparable visual quality. The catch is that this rarely happens on its own. On PrestaShop 8, WebP generation exists but ships as an experimental option that is off out of the box, so it commonly stays off. On the older 1.6 and 1.7 versions there is no native support at all, and serving WebP means adding a module many merchants never install. Either way the result is the same: a merchant uploads a perfectly good photo, and the store ships it to every visitor several sizes heavier than it needs to be.
It is the most boring kind of performance problem, which is exactly why it survives. Nobody looks at a product photo and thinks the format is wrong. The image looks fine. The weight is invisible.
What the benchmark shows
The data makes the scale of it clear. Nearly two-thirds of the PrestaShop stores we scanned, 12,371 of them, were serving images in legacy formats rather than WebP, the most common PrestaShop-specific speed failure in the whole benchmark.
That fits the larger picture. PrestaShop carried the widest modernization gap of any platform we measured, with the lowest baseline scores and the highest share of stores in the benchmark’s lowest maturity tier. (The 2026 platform benchmark has the detail.) Image format is the single most common piece of that gap, and the cheapest to close.
Why it stays that way
Enabling modern image formats is usually a one-time technical step, with a catch worth knowing: switching the setting on only affects images uploaded after that point. The photos already in your catalog, often the bulk of them, stay in their old format until a regeneration converts them too. So a store can have the setting switched on and still serve legacy images for years. It is not hard work, but it is the kind of task that never reaches the top of anyone’s list, because the store is working and the photos look right. Older stores often never had the option, and were never revisited once they did. The same goes for lazy loading, the related setting that tells the browser to load images as the shopper scrolls rather than all at once. The two problems usually travel together.
How to find what’s slowing your PrestaShop store
The fix is narrow and worth it. In practice that means checking:
- whether your product images are served as WebP or a modern equivalent, rather than legacy JPEG and PNG;
- whether the older images in your library were ever regenerated after the setting was turned on;
- whether images load lazily instead of all at once;
- whether they are sized for how they actually display, rather than uploaded at full resolution.
Why image weight matters for conversion and ranking is covered in the site speed guide; the part specific to PrestaShop is that the modern format is there for the taking and most stores have not taken it.
The same check that flagged those 12,371 stores across the benchmark is the one a scan runs on a single store, telling you whether your images are served as WebP or still in a legacy format, so you do not have to guess whether they are the reason it loads slowly.