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Google Analytics cookies and identifiers
Google Analytics mainly uses first-party cookies to report on visitor (aka. user) interactions on Google Analytics customers’ websites. Users may disable cookies or delete any individual cookie. Learn more

In addition, Google Analytics supports an optional browser add-on that – once installed and enabled – disables measurement by Google Analytics for any site a user visits. Note that this add-on only disables Google Analytics measurement.

Where a site or app uses Google Analytics for Apps or the Google Analytics for Firebase SDKs, Google Analytics collects an app-instance identifier — a randomly generated number that identifies a unique installation of an App. Whenever a user resets their Advertising Identifier (Advertising ID on Android, and ID for Advertisers on iOS), the app-instance identifier is also reset.

Where sites or apps have implemented Google Analytics with other Google Advertising products, like Google Ads, additional advertising identifiers may be collected. Users can opt-out of this feature and manage their settings for this cookie using the Ads Settings. Learn more

Google Analytics also collects Internet Protocol (IP) addresses to provide and protect the security of the service, and to give website owners a sense of which country, state, or city in the world their users come from (also known as "IP geolocation"). Google Analytics provides a method to mask IPs that are collected (detailed below) but note that website owners have access to their users’ IP addresses even if the website owners do not use Google Analytics.
Data Collected by Google Analytics
First-party Cookies
Google Analytics collects first-party cookies, data related to the device/browser, IP address and on-site/app activities to measure and report statistics about user interactions on the websites and/or apps that use Google Analytics. Customers may customize cookies and the data collected with features like cookie settings, User-ID, Data Import, and Measurement Protocol. Learn more
Google Analytics customers who have for instance, enabled the analytics.js or gtag.js collection method can control whether or not they use cookies to store a pseudonymous or random client identifier. If the customer decides to set a cookie, the information stored in the local first-party cookie is reduced to a random identifier (e.g., 12345.67890).
For customers who use the Google Analytics for Apps SDK, we collect an App Instance Identifier, which is a number that is randomly generated when the user installs an app for the first time.
Advertising identifiers
Where customers use Google Analytics Advertising Features, Google advertising cookies are collected and used to enable features like Remarketing on the Google Display Network. These features are subject to the users’ Ads Settings, the Policy requirements for Google Analytics Advertising Features and Google’s EU User Consent policy, which requires customers to obtain consent for cookies where legally required—including consent for personalized ads. For more information about how Google uses advertising cookies, visit the Google Advertising Privacy FAQ. It is possible to implement Google Analytics without affecting normal data collection where Advertising features are disabled until consent is obtained.
IP Address
Google Analytics uses IP addresses to derive the geolocation of a visitor, and to protect the service and provide security to our customers. Customers may apply IP masking so that Google Analytics uses only a portion of an IP address collected, rather than the entire address. In addition, customers can override IPs at will using our IP Override feature.
PII Prohibition
Our contracts prohibit customers from sending Personally Identifiable Information to Google Analytics. Customers should follow these Best Practices to ensure PII is not sent to Google Analytics.

See https://support.google.com/analytics/answer/6004245?hl=en for more information