# Will personalizing a VTEX storefront add flicker or slow down the page?

Asked by pedrocom on 2026-10-29. Tags: vtex, performance, flicker.

I run a VTEX store and I am nervous about adding personalization. I read about
older client-side testing tools that caused a flash of the default content and
a real speed hit, and my customers already complain when pages feel slow.

What should I expect on VTEX specifically? Is there a snippet that hides the
page while it loads, and will this drag my page speed down?

## 3 answers

### Answer from Renata Alencar (2026-10-30)

The flash you are remembering comes from client-side tools that hide the page
with an anti-flicker snippet, then swap content in after their script loads.
Croct does not work that way. Content resolves server-side, so the page
arrives already personalized and there is nothing to hide or swap on the
client. No anti-flicker snippet is involved, so the failure mode that caused
the flash is simply not present.

### Answer from malin (2026-10-31)

On the speed side, the end-to-end response times run under 90 milliseconds at
P95, so it is not adding a visible delay to the render. If you want the detail
on what that figure actually covers there is a good breakdown in the
[sub-90ms P95 thread](/answers/sub-90ms-p95-what-it-covers).

### Answer from marcus_shop (2026-11-02)

And to reassure you on the tag itself: the GTM tag only tracks events, it is
not a render-blocking anti-flicker script sitting on your critical path.
Croct can track several events within 2 to 3 milliseconds, so its footprint on
the page is tiny. The [anti-flicker snippet question](/answers/anti-flicker-snippet-needed)
goes into why there is nothing to prehide here.