Data collection (client-side)

To learn which data Kameleoon stores on its backend servers—primarily for analytics and reporting—read the data collection back-end article.

Introduction

Like any web analytics solution, Kameleoon collects data such as URLs visited, browser version, and time spent on your website. As an experimentation and personalization platform, Kameleoon also requires real-time, persistent access to this data to trigger experiments and personalization campaigns with minimal latency. Because the JavaScript runtime environment resets on each page change, storing this data in memory alone is not possible. Instead, Kameleoon reads and writes data across different web pages (URLs). Fetching data from a backend server at the start of each page load is one alternative, but this approach has two drawbacks:

Performance cost: Each page load incurs an extra server call.
Scalability cost: Frequent server requests degrade performance at scale.

Local storage is a more efficient approach. It lets Kameleoon store data directly in the browser.

Local storage as a data storage mechanism

Kameleoon does not use cookies to store data for two reasons:

Cookies are not designed to store large amounts of data.
The browser sends cookies with every HTTP request, including requests for static resources such as images, which increases bandwidth usage and reduces performance.

Instead, Kameleoon uses Local Storage, a standard web technology that most browsers support. It works similarly to cookies but supports much larger storage capacity (typically a few MBs, depending on the browser). Compared to cookies, Local Storage has the following properties:

Only JavaScript can write to Local Storage—servers cannot.
Only JavaScript can read data from Local Storage.
The browser never sends Local Storage data to remote HTTP servers, which makes it more secure.

However, Local Storage has one key limitation: it is scoped to a single exact subdomain.

Local storage limitations for unified session data

Unlike cookies—where a script on http://www.example.com can create a cookie accessible from buy.example.com—Local Storage is partitioned by subdomain and protocol. For example, if your e-commerce website is hosted on https://www.randomshop.com but your conversion funnel runs on https://transaction.randomshop.com, Local Storage cannot share data between these two subdomains. This can produce inconsistent experiment variations across the customer journey, affecting both user experience and experiment validity. Kameleoon provides a mechanism to unify session data across subdomains. For details, see Unify session data across subdomains.

List of collected data

This page covers two categories of data:

Data collected and stored for all visitors (excluding visitors who opted out).
Data collected for internal use when Kameleoon users build experiments on the platform.

For data privacy purposes, focus on the first category. The second category applies only to a small number of internal employees.

Kameleoon always stores data in a first-party context, associated with your domain. Kameleoon never stores third-party data on Kameleoon-owned domains.

Data stored for all visitors

Data stored in Local Storage

Local Storage does not have a built-in expiration mechanism. To work around this, Kameleoon emulates lifespan expiration by storing data with two fields:

"value": The stored information.
"expirationDate": A timestamp that defines when Kameleoon stops using the data.

Example:

kameleoonLegalConsent: {"value": {"AB_TESTING": true, "PERSONALIZATION": true},"expirationDate":1545297630228}

Application File (engine.js)
JavaScript SDK

Key	Description	Lifespan
`kameleoonVisitorCode`	Unique Kameleoon visitorCode identifier.	365 days
`kameleoonData`	Visitor and session data (for example, browsing history and session info). Kameleoon stores this data in Local Storage using a simple encoding scheme. The full list of data this key contains appears below.	365 days
`kameleoonExperiment-${experimentId}`	Experiment variation allocation and assigned variation ID (either “Reference”, the variation ID, or “none” if traffic exclusion is configured), and the date Kameleoon assigned the variation.	30 days (renews on revisit)
`kameleoonPersonalization-${personalizationId}`	The personalization variation allocation for this visitor.	30 days (renews on revisit)
`kameleoonGlobalPersonalizationExposition`	The visitor’s global exposition status for all personalizations. A value of `"false"` prevents this visitor from seeing any personalization. A value of `"true"` allows exposure when the visitor meets the required targeting conditions. By default, no global traffic exclusion applies. You can configure this value in the project configuration settings.	365 days
`kameleoonLegalConsent`	Legal consent for the use of Kameleoon. The value format is, for example, `{"AB_TESTING": true, "PERSONALIZATION": false}` or `{"PERSONALIZATION": true}`.	365 days
`kameleoonOpenTabs`	IDs of open tabs on the same website.	365 days
`KameleoonProducts_device_id`	A unique device ID for the visitor. Kameleoon only stores this key if you have the Product Recommendation add-on.	365 days
`kameleoonRequestEvents`	Failed requests that Kameleoon cannot send when the page reloads immediately. This behavior is specific to Safari.	Deleted once the page reloads.

The kameleoonData key stores the following data for each visit (on this device only, or all visits if you use cross-device history reconciliation):

Custom data
Device type (mobile, tablet, or desktop)
Operating system
Browser name and version
Screen size
Window size
Browser time zone
Browser language
Original referrer (acquisition channel)
Number of pages viewed
Title and URL of pages visited
Time spent on the website
Visit start and end time
Number of open tabs
Whether an ad blocker is active
List of conversions (clicks, transactions, and other events)
List of personalizations and A/B experiments the visitor saw
Current weather conditions (if the targeting condition is active): temperature, wind, rain, and other conditions
Sunset time (if a weather targeting condition is active, because some weather criteria require it)
Weather forecast (if the targeting condition is active): temperature, wind, rain, and other conditions
Geolocation (if a geolocation or weather targeting condition is active)
IP address (if the targeting condition is active)
External segmentation data from a third-party DMP or CRM
Products seen (if the Product Targeting add-on is enabled)

Key	Description	Lifespan
`kameleoonClientData`	A local copy of the remote configuration file the SDK fetches. It contains configuration details for live feature flags.	Until removed manually or by browser settings.
`kameleoonConsentData`	Legal consent for Feature Experiments obtained from the visitor.	targetingDataCleanupInterval
`kameleoonDataInfo`	Technical information for data cleanup and linked visitor sessions. Required for cross-device experimentation.	Until a tracking request succeeds.
`kameleoonForcedExperimentVariation`	A specific experiment variation required for custom evaluation of a given feature flag.	targetingDataCleanupInterval
`kameleoonForcedFeatureVariation`	Specific feature variations used for simulation of a given feature flag.	Session
`kameleoonTargetingData`	Visitor and session data, including browsing history and session details, required for targeting purposes.	targetingDataCleanupInterval
`kameleoonTrackingData`	All visitor codes on this browser for tracking requests.	Until a tracking request succeeds.
`kameleoonVariationData`	Assigned variations for each feature flag, used to maintain visitor consistency across sessions.	targetingDataCleanupInterval

The kameleoonTargetingData key stores the following data associated with the visitor:

Custom data
Conversion
Page view
Unique identifier
Geolocation data
User agent
Browser
Device
Cookie
Kameleoon conversion score (AI Predictive Targeting)
Operating system
Application version
Visits data
Personalization

Data stored in Session Storage

Key	Description	Lifespan
`kameleoonDisabledForVisit`	Disables Kameleoon for the current visit. Kameleoon sets this key when you enable the Disable Kameleoon for the entire visit timeout option.	Session duration
`kameleoonAnalyticsTrackingTimes`	Optimizes the number of third-party analytics tracking calls Kameleoon makes when you use a web analytics integration.	Session duration
`kameleoonTabId`	A unique 8-digit identifier that distinguishes a browser tab and prevents redundant tracking of the same page URL across multiple triggered events.	Session duration
`kameleoonActiveScript`	Kameleoon sets this value when the script confirms it is installed on the page.	Session storage value

Data stored in cookies

Application File (engine.js)
JavaScript SDK

Kameleoon uses only one cookie to store a randomly generated visitor identifier. The Kameleoon CDN may also set an optional cookie when it delivers the application file, unless you self-host the application file.If you use the Kameleoon Product Recommendation add-on, Kameleoon stores two additional cookies. You can contact your Customer Success Manager to enable a cookieless option that stores these data points in Local Storage instead.

Key	Description	Lifespan
`KameleoonProducts_session_code`	A unique session identifier.	Session duration
`KameleoonProducts_session_last_act`	The timestamp of the last activity.	1 hour

Key	Description	Lifespan
`_detectRootDomain`	Temporary test cookie (value=`testRootDomain`) that Kameleoon uses to detect the main domain of the site.	Deleted immediately after use.
`kameleoonVisitorCode`	The unique Kameleoon visitorCode identifier.	365 days
`kameleoonReferrer`	Temporary cookie for redirect URL experiments. Kameleoon stores the `document.referrer` value before the redirect occurs.	Deleted immediately after use.
`kameleoonSimulationFFData`	Data required to simulate a specific variation of a feature flag.	Session

Temporary data stored only for Kameleoon internal use

Data stored in cookies

Key	Description	Lifespan
`kameleoonSimulationParameters`	Kameleoon Simulation Mode uses this cookie to enable simulation across subdomains. Without it, simulation does not work correctly if your site has subdomains. All simulation query parameters must be included in URL-encoded JSON format using `JSON.stringify`. For example:
`KEY - kameleoonSimulationParameters`, `VALUE - {"kameleoon-experiment-id":"266118","kameleoon-simulation":"true","kameleoon-language":"en"}`	1 hour, but deleted immediately when the simulation is closed.

Data stored in Local Storage

Key	Description	Lifespan
`kameleoonSimulation`	Data required for simulation purposes.	1 hour
`kameleoonSimulationShortURL`	The short URL of the simulation.	1 hour
`kameleoonSimulationVisitorData`	All virtual data about the visitor and their visits, used for simulation purposes.	1 hour

Data stored in Session Storage

Key	Description	Lifespan
`kameleoonFullApplicationCode`	The entire Kameleoon codebase, required for simulation. The production application file is size-optimized and does not include all code, so Kameleoon stores the full version here.	1 hour
`kameleoonVariation-${variationId}`	Variation code and data for preview or simulation purposes.	1 hour
`kameleoonRedirectionURL`	The absolute URL of the page when Kameleoon triggers a redirect experiment. Kameleoon stores this to prevent infinite redirect loops.	Removed when the visitor navigates to a different page.

Home

Web experimentation

Feature experimentation

Core concepts

Privacy and compliance

Developer tools

Introduction

Local storage as a data storage mechanism

Local storage limitations for unified session data

List of collected data

Data stored for all visitors

Data stored in Local Storage

Data stored in Session Storage

Data stored in cookies

Temporary data stored only for Kameleoon internal use

Data stored in cookies

Data stored in Local Storage

Data stored in Session Storage

​Introduction

​Local storage as a data storage mechanism

​Local storage limitations for unified session data

​List of collected data

​Data stored for all visitors

​Data stored in Local Storage

​Data stored in Session Storage

​Data stored in cookies

​Temporary data stored only for Kameleoon internal use

​Data stored in cookies

​Data stored in Local Storage

​Data stored in Session Storage

Introduction

Local storage as a data storage mechanism

Local storage limitations for unified session data

List of collected data

Data stored for all visitors

Data stored in Local Storage

Data stored in Session Storage

Data stored in cookies

Temporary data stored only for Kameleoon internal use

Data stored in cookies

Data stored in Local Storage

Data stored in Session Storage