---
title: Track Event for the Swift SDK
slug: feature-experimentation/docs/track-event-swift
docTags: 
createdAt: 2026-08-05T20:39:54.000Z
---

Tracks a conversion event for a user. In other words, tracks an action a user takes. Logs an error message if the specified event key does not match any existing events. See [How Optimizely Experimentation counts conversions](#).

## Version

SDK 3.7 and higher. See [Minimum version support](docId:2shbZfPCkPAZ0mlZpL1TU).

## Description

Use this method to track events across multiple flag rules for a user. You should only make one track call per conversion (user action), even if many rules are measuring the conversion.

You call the `trackEvent` method on a user. For information about the user object, see [OptimizelyUserContext for the Swift SDK](docId\:lx6nIl7h8TioF9Dj8FS5t).

:::hint{type="warning"}
The attributes passed to `trackEvent` are *only* used for [results segmentation](docId:_K6n7h_MZ8b0xn6yWPrrq) on the [Optimizely Experiment Results page](docId\:mrUblIuNVOZc1dvjWdsbw).
:::

## Parameters

- `eventKey` (required) – String – The key of the event to be tracked. This key must match the event key provided when the event was created [in the Optimizely app](docId\:Bf3o37J3IJTUuVR7GshGd) or [REST API](docId\:NxpGs0D4LibV6Jp26feiJ).
- `eventTags` (optional) – Map – A map of key-value pairs specifying the [reserved tag keys](docId\:TPYh_YgbEQNnWIXKthzhl) names and their corresponding values for this particular event occurrence. `eventTags` are contextual metadata about [conversion events](docId\:onBazDzYYz526tL9aQF0s). For example, revenue, load time, or total value. The following are available tag keys:
  - `revenue` – An integer value that is used to track the revenue metric for your experiments, aggregated across all conversion events. `revenue` is recorded in cents.
  - `value` – A floating point value that is used to track a custom value for your experiments. Use this to pass the value for numeric metrics.
  - `$opt_event_properties` –   A map of default and custom event properties and their values.

See [reserved event tags](docId\:TPYh_YgbEQNnWIXKthzhl).

## Returns

This method sends conversion data to Optimizely Feature Experimentation. It does not provide return values.

## Example

```swift
let user = optimizely.createUserContext(userId: "user123", attributes: ["logged_in": true])

// Event properties
let properties: [String: Any] = [
    "category": "shoes",
    "Text": "value"
]

// Event tags
let tags: [String: Any] = [
  "revenue": 100000,
  "value": 100.00,
  "$opt_event_properties": properties
]

//trackEvent(eventKey (required), eventTags (optional))
try? user.trackEvent(eventKey: "my_purchase_event_key", eventTags: tags)
```

## Side effects

Additional Feature Experimentation functionality may be triggered by using this method.

### Conversions

Calling this method records a conversion and attributes it to the variations that the user has seen. See [How Optimizely Experimentation counts conversions](docId\:onBazDzYYz526tL9aQF0s).

You can create [metrics](docId\:e2qGf29S6pO8SW90_IVuH) on this conversion event and add metrics to experiments even after the conversion is tracked. See [Events: Tracking clicks, pageviews, and other visitor actions](docId\:puGm9z4XkEG5PDkyaNmlA).

:::hint{type="danger"}
This method does not track events if the event key is invalid.

Changing the traffic allocation of running experiments affects how conversions are recorded and variations attributed to users. See [Why you should not change a running experiment](docId\:IsU8ejnD3mrkAia2mtIOA).
:::

### Notification listeners

Accessing this method triggers a call to the [track notification listener](docId\:PaUUiwg7zYOguMb_HrFGN).

:::hint{type="danger"}
This method does not call the `TRACK` notification listener if the event key is invalid.
:::

## Source files

The language and platform source files containing the implementation for Swift are available on [GitHub](https://github.com/optimizely/swift-sdk/blob/master/Sources/Optimizely/OptimizelyClient.swift).