Jetpack's built-in visitor analytics. It records page views, referring sites, search terms, and outbound link clicks, and also carries the shared visitor-tracking library used by Jetpack Instant Search and WooCommerce Analytics.
Service URL: automattic.com (opens in a new window)
tk_tc
Used once per page load to work out which cookie domain the Tracks library should use, then removed as soon as it's read back.
Session (deleted immediately after use)
tk_aip
Stores a list of anonymous visitor IDs so they can be merged into one identity once a visitor is recognized.
Up to 5 years
tk_ai
Stores a randomly-generated anonymous visitor ID so Jetpack's Tracks analytics library can link tracking events to the same visitor.
Session in wp-admin; up to 5 years on the frontend
tk_qs
Queues analytics events for Jetpack's Tracks library so none are lost if the page closes before they can be sent.
30 minutes
My better half looked skeptical when I presented him with a lovely bowl of plain oatmeal topped with a perfectly fried egg