Merge pull request #4232 from segmentio/joeynmq-patch-3

Add info for cookies that set by Analytics.js

Author: rchinn1

src/connections/sources/catalog/libraries/website/javascript/index.md

@@ -791,10 +791,10 @@ Segment loads the libraries required for your **enabled** Destinations. When you
 
 Using Analytics.js doesn't offer a large performance benefit, but is more performant than installing each of the destinations individually. And as more destinations move to accept data directly from Segment, you'll receive more performance benefits automatically.
 
-One option, if you don't want to use any bundled third-party tools, is to use the [Analytics-Node](https://github.com/segmentio/analytics-node) package. 
+One option, if you don't want to use any bundled third-party tools, is to use the [Analytics-Node](https://github.com/segmentio/analytics-node) package.
 
 > info ""
-> Analytics.js doesn't set third-party cookies and only sets first-party cookies. 
+> Analytics.js doesn't set third-party cookies and only sets first-party cookies.
 
 ### Bundle size
 
@@ -804,6 +804,27 @@ The snippet asynchronously requests and loads a customized JavaScript bundle (`a
 
 Without any destinations enabled, the `analytics.min.js` file is about 62KB. Each time you enable a destination, the file's size may increase slightly.
 
+### Cookies set by Analytics.js
+
+Segment sets three cookies in general:
+
+| Cookie             | Description                                                                       |
+| ------------------ | --------------------------------------------------------------------------------- |
+| `ajs_anonymous_id` | An anonymous ID generated by Analytics.js, used for Segment calls.                |
+| `ajs_group_id`     | A group ID that can be specified by making a `group()` call with Analytics.js.    |
+| `ajs_user_id`      | A user ID that can be specified by making an `identify()` call with Analytics.js. |
+
+For Google Chrome, these cookies expire by default **one year** after the date created. Other [supported browsers](/docs/connections/sources/catalog/libraries/website/javascript/supported-browsers/) might have a different expiration time.
+
+Some user/group traits are also stored in `localStorage`:
+
+| Cookie                 | Description                                         |
+| ---------------------- | --------------------------------------------------- |
+| `ajs_user_traits`      | The traits that are passed in an `identify()` call. |
+| `ajs_group_properties` | The properties that are passed in a `group()` call. |
+
+Note that `localStorage` variables don't expire because the browser defines that functionality.
+
 ### Local storage cookies used by Analytics.js
 
 Analytics.js uses `localstorage` cookies if you have retries enabled, to keep track of retry timing.