> ## Documentation Index
> Fetch the complete documentation index at: https://docs.aloftly.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Traffic source sessions

> GA4 sessions retained as a source-breakdown series.

| Contract           | Value                            |
| ------------------ | -------------------------------- |
| Metric key         | `ga4.traffic_source`             |
| Source             | Google Analytics 4               |
| Status             | supporting                       |
| Type               | source                           |
| Semantic version   | 1                                |
| Catalog visibility | Supporting or fixed-surface only |

## How it's calculated

```text theme={null}
value = GA4 sessions copied into the acquisition breakdown series for each channel/source/medium/device tuple.
```

### Built from

* `GA4 Data API sessions`
* `sessionDefaultChannelGroup`
* `sessionSource`
* `sessionMedium`

## Known caveats

* Semantically overlaps ga4.sessions; kept for existing breakdown contracts.

## Where this appears

* Traffic source breakdowns

<AccordionGroup>
  <Accordion title="Grain and identity" icon="ruler">
    daily\_snapshot; entity: traffic\_segment; same-day fold: sum; additivity: semi\_additive.

    **Join and identity keys**

    * propertyId
    * snapshotDate
    * channel
    * source
    * medium
    * device
  </Accordion>

  <Accordion title="Filters and boundaries" icon="filter">
    * Organization, store, and GA4 property are resolved server-side.
    * Reads use a half-open interval: recorded\_at >= start and recorded\_at \< end.
    * Site reports preserve acquisition/device segments; page reports retain the top 75 pages per day.
  </Accordion>

  <Accordion title="Timezone, currency, and freshness" icon="clock">
    **Timezone.** GA4 report dates are property-calendar dates normalized to UTC-midnight labels. They are not rebucketed in the browser timezone.

    **Currency.** Not applicable.

    **Freshness.** Daily scheduled sync.
  </Accordion>

  <Accordion title="Version history" icon="clock-rotate-left">
    | Date       | Change                                                             |
    | ---------- | ------------------------------------------------------------------ |
    | 2026-08-03 | Bound the metric to the executable certified semantic release.     |
    | 2026-07-27 | Registered GA4 traffic and page contracts in the semantic catalog. |
  </Accordion>
</AccordionGroup>