Persistent cookies are cookies with a defined validity period that remain stored in the browser even after it is closed. They can persist for days, months or even years.
How do persistent cookies work?
Persistent cookies have a set expiry time (Expires or Max-Age attribute). The browser stores them on disc and automatically deletes them once the specified period elapses.
Typical uses of persistent cookies
- Remember login – "Remember me" functionality
- User preferences – Language, currency, display
- Analytics – Identifying returning visitors
- Remarketing – Tracking for targeted advertising
- A/B testing – Consistent display of a variant
Persistent cookie validity periods
- Short-term – Hours to days (analytics)
- Medium-term – Weeks to months (preferences)
- Long-term – Months to years (remarketing)
Legal requirements
Most persistent cookies require user consent because they serve purposes beyond the basic functioning of the website. The GDPR recommends minimising retention periods – cookies should not last longer than necessary for the given purpose.