Data Storage in Cookies

Detailed technical documentation on persistent user data stored in cookies or local storage by the RudderStack’s JavaScript SDK.

By default, the RudderStack JavaScript SDK stores persistent user data in the cookies. If the cookies are not supported, local storage is used instead.

All the cookies are stored in the top-level domain by default. It helps you to identify the users visiting from websites hosted under a particular sub-domain. For example, if you include the JavaScript SDK in both admin.samplewebsite.com and app.samplewebsite.com, the SDK will store the cookie in samplewebsite.com. However, you can configure where you want to store the cookie by using the setCookieDomain parameter in the load API options as shown:

rudderanalytics.load(<WRITE_KEY>, <DATA_PLANE_URL>, {
  setCookieDomain: "samplewebsite.com",
});

Cookies

The list of cookies used by the JavaScript SDK to store persistent user data is mentioned below:

Name	Description	Example	Clearing mechanism using the SDK
rl_user_id	Stores the user ID set via the identify API. All the subsequent event payloads will contain this data unless cleared from the storage.	4578, USER_001	rudderanalytics.reset()
rl_trait	Stores the user traits object set via the identify API. All the subsequent event payloads will contain this data unless cleared from the storage.	{ email: "[e-mail]", accountType: "pro", country: "US", someObj: { key1: val1, key2: val2, }}	rudderanalytics.reset()
rl_anonymous_id	Stores the anonymous ID. By default, it would be the auto-generated unique ID by SDK for each visitor unless overridden via setAnonymousId API. All the subsequent event payloads will contain this data unless cleared from the storage.	5bfe258f-bd2f-49cf-bddd-8b844f74ab4b, customAnonId	rudderanalytics.reset(true)
rl_group_id	Stores the user group ID set via the group API. All the subsequent group event payloads will contain this data unless cleared from the storage.	GRP_3, 98	rudderanalytics.reset()
rl_group_trait	Stores the user group traits object set via the group API. All the subsequent group event payloads will contain this data unless cleared from the storage.	{ location: "New Orleans", nationality: "US", someObj: { key1: val1, key2: val2, }}	rudderanalytics.reset()
rl_page_init_referrer	Stores the initial referrer of the page when a user visits a site for the first time. All the subsequent event payloads will contain this data.	https://www.google.com/	Cannot be cleared using SDK.
rl_page_init_referring_domain	Stores the initial referring domain of the page when a user visits a site for the first time. All the subsequent event payloads will contain this data.	google.com	Cannot be cleared using SDK.
test_rudder_cookie	Checks whether the cookie storage of a browser is accessible or not. Once checked, this cookie is removed immediately.	test_rudder_cookie:true	Cleared automatically.

The cookie values are encrypted and their length is directly proportional to the values provided to the SDK. Also, all the cookie names are prefixed with rl_ and the values are prefixed with RudderEncrypt:. For example, rl_user_id —> RudderEncrypt:U2FsdGVkX1+UKmiooYoGmKdNws7sgmWgGfHe.

Local storage cookies

The local storage cookies are used by the JavaScript SDK to keep track of the events sent to the RudderStack backend. They are listed in the table below:

Name	Description	Example
ack	Timer for other browser tabs to claim control of the retry queue.	1639734070124
reclaimStart and reclaimEnd	Determines if a tab takes over the queue from another tab.	2dc2aee6-2836-4273-be69-79c90c04ddec
inProgress	Keeps track of the events in progress.	{ "d89d7fb5-945e-4378-bda5-492e4b596fb4": { "item": { "url": "https://rudderstack-dataplane.rudderstack.com/v1/track", "headers": { "Content-Type": "application/json", ... }, "message": { ... } "attemptNumber": 1, "time": 1639734792773, "id": "a4d89d7f-b594-4eb3-b8bd-a5492e4b596f" } }}
queue	Keeps track of the events that are in queue to be processed.	[ { "item": { "url": "https://rudderstack-dataplane.rudderstack.com/v1/track", "headers": { "Content-Type": "application/json", ... }, "message": { ... } "attemptNumber": 0, "time": 1639734792773, "id": "a4d89d7f-b594-4eb3-b8bd-a5492e4b596f" } }]

All the local storage cookie names are prefixed with rudder.<uuid>. For example, rudder.2dc2aee6-2836-4273-be69-79c90c04ddec.reclaimEnd.

FAQ

Refer to the FAQ section for solutions to some of the commonly faced issues while using the JavaScript SDK on your website.

Contact us

For more information or queries on this guide, you can contact us or start a conversation in our Slack community.