Does Klaviyo slow down a store?
In 7IT’s test of 367 US online stores, Klaviyo ran on 196 of them (53.4%). On the median store that loads it, it downloaded 219 KB and kept the phone busy for 0.15 s before the page could respond.
53.4%of 367 US stores run it
219 KBmedian download on stores that load it
0.15 smedian time the phone spends running it
Stores with it and without it.
| Stores | Median score | Main content | Blocking time | Apps on the page | |
|---|---|---|---|---|---|
| With Klaviyo | 196 | 34 | 12 s | 1243 ms | 22 |
| Without | 171 | 34 | 11.3 s | 1348 ms | 18 |
Stores that run Klaviyo had a median score of 34, against 34 for stores without it. They also run more apps overall (a median of 22 against 18), so that gap is not all Klaviyo’s doing. The size and phone time above are Klaviyo’s own. On this sample there is no score penalty that can be pinned on it.
One in four stores that load it download more than 340 KB of it, and spend more than 0.24 s running it. Median Google phone-lab results, home pages only, September 2026. Method and limits in the study.
If you run Klaviyo.
- Pop-up and sign-up scripts rarely need to run before the page appears. Load them after the first scroll or after a few seconds on the page.
- Do not show a pop-up on the first page a visitor from an ad lands on. It costs speed and the first impression at once.
- Keep the signup form on the page (footer, checkout) and let the script that draws the pop-up wait.