Does Microsoft Clarity slow down a store?
In 7IT’s test of 367 US online stores, Microsoft Clarity ran on 99 of them (27%). On the median store that loads it, it downloaded 29 KB and kept the phone busy for 0.13 s before the page could respond.
27%of 367 US stores run it
29 KBmedian download on stores that load it
0.13 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 Microsoft Clarity | 99 | 31 | 13.2 s | 1550 ms | 25 |
| Without | 268 | 36 | 11.2 s | 1098 ms | 18 |
Stores that run Microsoft Clarity had a median score of 31, against 36 for stores without it. They also run more apps overall (a median of 25 against 18), so that gap is not all Microsoft Clarity’s doing. The size and phone time above are Microsoft Clarity’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 29 KB of it, and spend more than 0.17 s running it. Median Google phone-lab results, home pages only, September 2026. Method and limits in the study.
If you run Microsoft Clarity.
- Session replay and heatmaps record every visitor. Sample a share of sessions instead of all of them.
- Start recording after the page is idle, not during the first paint.
- Turn it off when the question you installed it for is answered.