Does Google Tag Manager slow down a store?
In 7IT’s test of 367 US online stores, Google Tag Manager ran on 274 of them (74.7%). On the median store that loads it, it downloaded 526 KB and kept the phone busy for 0.51 s before the page could respond.
74.7%of 367 US stores run it
526 KBmedian download on stores that load it
0.51 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 Google Tag Manager | 274 | 32 | 12.6 s | 1532 ms | 24 |
| Without | 93 | 48 | 10.2 s | 459 ms | 9 |
Stores that run Google Tag Manager had a median score of 32, against 48 for stores without it. They also run more apps overall (a median of 24 against 9), so that gap is not all Google Tag Manager’s doing. The size and phone time above are Google Tag Manager’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 699 KB of it, and spend more than 0.84 s running it. Median Google phone-lab results, home pages only, September 2026. Method and limits in the study.
If you run Google Tag Manager.
- A tag manager is a container: its cost is the cost of every tag inside it. Open the container and list each tag with an owner and a reason.
- Delete tags for campaigns, agencies and tools you no longer use. Most containers carry several.
- Fire tags that do not need the first second (heatmaps, secondary pixels) on the first interaction or a few seconds after load.