Cookie Lifetime
Cookie lifetime is the period during which a cookie file is stored in a user’s browser and can be used by a website or advertising system to identify that user. Simply put, it’s the duration a browser “remembers” a person after their visit to a site.
What is a Cookie?
A cookie is a small file that a website saves in the user’s browser. It can store information about:
- The session
- The selected language
- Cart contents
- The traffic source
- User actions
- Advertising tags
What Types of Cookie Lifetimes Exist?
- Session Cookies
Stored only during the current visit. They are automatically deleted after the browser is closed. - Persistent Cookies
Stored on the user’s device for a specified period:- Several days
- A month
- 90 days
- A year or more
The duration is set when the cookie is created.
Why is Cookie Lifetime Important?
The storage duration directly affects:
- The accuracy of ad attribution
- The effectiveness of retargeting
- The analysis of repeat visits
- Conversion calculation
- The collection of user statistics
For example, if an advertising campaign’s cookie lasts 30 days, but a user makes a purchase after 45 days, the sale might not be attributed to that channel.
How Does it Impact Analytics and Marketing?
- Attribution
The longer the cookie lifetime, the higher the chance a channel gets “credit” for a sale. - Retargeting
If the lifetime is short, the user stops seeing ads after it expires. - Analytics
Too short a lifetime can underreport return visits and repeat purchases.
Typical Lifetimes in Advertising
Advertising systems often use:
- 7 days — for short sales cycles
- 30 days — standard for e-commerce
- 90 days — for longer cycles
- 180–365 days — for complex B2B products
The optimal duration depends on the decision-making time in a specific niche.
Limitations and Modern Changes
Today, cookie lifetime is affected by:
- Browser settings
- Operating system restrictions
- Personal data legislation requirements
- Blocking of third-party cookies
Some browsers automatically shorten the storage duration of third-party cookies, making accurate attribution more difficult.
Typical Mistakes
- Using too short a lifetime for a long sales cycle.
- Ignoring the differences between first-party and third-party cookies.
- Evaluating advertising effectiveness without considering the actual decision-making period.
Key Takeaway
Cookie lifetime determines how long a system can track user actions after a visit. The accuracy of analytics, the correct attribution of advertising channels, and the effectiveness of retargeting all depend on choosing the right duration.
