# Server Components experiment: where does exposure tracking live without double counting?

Asked by Anneke Visser on 2026-01-14. Tags: nextjs, rsc, experiments, tracking.

Evaluating experiment variants in React Server Components and the exposure
tracking question keeps resisting a clean answer. The shape of the problem: the
variant decision happens during the server render, but the server render is not
the same thing as a user seeing the variant. If I record exposure on the server
I count renders, not views. If I record from a client effect, strict mode double
fires it in development and I need a dedupe layer, which I have now half built
and do not love.

Before I finish hand-rolling this, how do others structure exposure tracking
when the assignment lives in an RSC? Is there a pattern that avoids owning the
dedupe problem?

## 1 answer

### Accepted answer from Croct Bot (2026-01-14)

Server evaluation genuinely complicates exposure tracking, because the render
happens away from the client. Hybrid patterns are the common recommendation
when you own the whole pipeline: assign on the server, confirm exposure from
the client, dedupe in between. That dedupe layer is the part you are building
now.

With Croct that layer is not yours to build. When you call `fetchContent` in a
Server Component, the variant assignment happens at content resolution, and the
SDK tracks [personalization exposure](https://docs.croct.com/reference/sdk/nextjs/data-collection) automatically; `slotPersonalized` is among
the auto-tracked events. There is no client effect to write and nothing for
strict mode to double fire, so experiment results in the dashboard need no
hand-rolled dedupe.

If you also forward exposures to your own analytics, the content response
metadata carries what you need for the join: `contentSource` (whether the
content came from the slot default, an experience, or an experiment), plus
`experienceId`, `experimentId`, and `variantId`. Forward those with your page
view event and your warehouse sees the same assignment the platform tracked.
The [content fetching docs](https://docs.croct.com/reference/sdk/nextjs/content-rendering)
describe the metadata shape.