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

# Unique Add to Carts: Session-Deduplicated Cart Events

> Track unique add to cart events deduplicated by session. Measure how many sessions included at least one add-to-cart action.

<Tip>
  Unique Add to Carts counts the number of sessions where at least one product was added to the cart, regardless of how many items were added during that session.
</Tip>

## Formula

<Info>
  **Unique Add to Carts** = **COUNT** ( Sessions with Add to Cart )
</Info>

### Formula Components

| Metric                        | Definition                                                           |
| ----------------------------- | -------------------------------------------------------------------- |
| **Sessions with Add to Cart** | Count of distinct sessions that fired at least one add-to-cart event |

| Metadata        |                         |
| --------------- | ----------------------- |
| **Type**        | Number                  |
| **Data Source** | [Upstack Pixel](/pixel) |
| **Aggregation** | Count                   |

***

## Example

Your store had **2,847 unique add-to-carts** last week, meaning 2,847 separate visitor sessions included at least one add-to-cart action.

| Day       | Total Add to Carts | Unique Add to Carts | Avg. Items per Session |
| --------- | ------------------ | ------------------- | ---------------------- |
| Monday    | 1,245              | 892                 | 1.4                    |
| Tuesday   | 1,156              | 834                 | 1.4                    |
| Wednesday | 1,389              | 1,121               | 1.2                    |

In this example, Monday had 1,245 total add-to-cart events but only 892 unique sessions with add-to-carts — some visitors added multiple products during their session.

***

## How It Works

Each session can fire multiple add-to-cart events when visitors add different products or quantities. Unique Add to Carts deduplicates these events at the session level, counting each session only once regardless of how many items were added. This gives you a cleaner view of shopping intent without inflation from multi-item carts.

***

## When to Use

| Scenario                              | Action                                                                                                         |
| ------------------------------------- | -------------------------------------------------------------------------------------------------------------- |
| Measuring true shopping intent        | Use Unique Add to Carts to see how many sessions showed purchase intent                                        |
| Comparing funnel stages               | Pair with [Unique Sessions](/reference/metrics/funnel/awareness/unique-sessions) for accurate conversion rates |
| Evaluating product page effectiveness | Compare against View Contents to measure add-to-cart rate                                                      |
| Analyzing multi-product behavior      | Compare against total Add to Carts to understand cart composition                                              |

***

## Related Metrics

| Metric                                                                        | Relationship                                         |
| ----------------------------------------------------------------------------- | ---------------------------------------------------- |
| [Add to Carts](/reference/metrics/funnel/engagement/add-to-carts)             | Total count including multiple events per session    |
| [Add to Cart Rate](/reference/metrics/funnel/engagement/add-to-cart-rate)     | Percentage of product views resulting in add-to-cart |
| [View Contents](/reference/metrics/funnel/engagement/view-contents)           | Product page views — the previous funnel step        |
| [Initiate Checkouts](/reference/metrics/funnel/engagement/initiate-checkouts) | Checkout starts — the next funnel step               |

[See all Engagement metrics →](/reference/metrics/funnel/engagement)