---
title: Track dynamic variables - iOS
description: Learn how to track and analyze variable metrics over time in your iOS app using the CSQ SDK
lastUpdated: 16 March 2026
source_url:
  html: https://docs.contentsquare.com/en/csq-sdk-ios/experience-analytics/track-dynamic-variables/
  md: https://docs.contentsquare.com/en/csq-sdk-ios/experience-analytics/track-dynamic-variables/index.md
---

*Dynamic variables* are additional information on the session that can be used to *segment sessions*.

For example, they can include information on the A/B Test variations displayed to the current user.

## Limits

### On the server side

* It is possible to save up to 40 distinct *dynamic variable keys* per screenview. If more are received, only the first 40 keys will be kept.
* If you are using the same key twice on the same screenview, the last value associated with the key will be collected.

### On the SDK side

* Every dynamic variable is composed of a pair of key (max. 512 characters) and value (max. 255 characters string or number of type `Long` between 0 and 232 - 1). In case these maximums length are reached, the SDK will automatically trim the exceeding characters.
* If key or value are empty, the SDK will instead send the literal string "cs-empty".

## Defining dynamic variables

To define and send a dynamic variable, directly use the key and String/Long value:

* Swift

  ```swift
  CSQ.addDynamicVar("cart_value", 123);
  CSQ.addDynamicVar("user_account_status", "premium");
  ```

* Objective-C

  ```objective-c
  [CSQ addDynamicVar:@"cart_value" value:@123];
  [CSQ addDynamicVar:@"user_account_status" value:@"premium"];
  ```

**Type of the value** — The value can be either a **whole number** or a **string**. For each case, available features won't be the same in the Contentsquare app:

* For **whole numbers**, you will be able to do some algebra. Example: *sessions with dynamic variable key = "numberOfFriends" and value >= 10*
* For **strings**, auto-completion and Regular Expression will be available. Example: *sessions with dynamic variable key = "accountType" and value = "Premium"*

## Sending a dynamic variable for each session

You may want to send a dynamic variable for each session (like the user's country or store). While **triggering the dynamic variable at app launch will cover most cases, it will not be enough**. A session can start when the app is put in foreground, after staying in background for more than 30 minutes. See [Session definition](../data-collection/#session-definition) section for more information.

That is why we also recommend **sending such dynamic variable every time the app enters foreground**.

You can use [`didBecomeActiveNotification` notification ↗](https://developer.apple.com/documentation/uikit/uiapplication/1622953-didbecomeactivenotification) and [`sceneDidBecomeActive(_:)` callback ↗](https://developer.apple.com/documentation/uikit/uiscenedelegate/3197915-scenedidbecomeactive) to detect foreground and trigger a dynamic variable.