Glossary
Cookie window
How long a tracking cookie stays valid after a browser stores it. When the cookie expires, a returning visitor can no longer be linked to the earlier click.
Also called: cookie duration, cookie lifetime
A cookie window is a storage question: how long does this cookie survive before the browser discards it?
An attribution window is a reporting question: how long after an interaction will the report still credit that interaction?
The two get used interchangeably and they are not the same. A cookie can outlive the window that would have credited it, and a conversion can fall inside an attribution window even though the cookie that identified the user is long gone. Affiliate programmes usually mean the first when they advertise a generous cookie window; ad platforms usually mean the second.
The complication is that the browser has the final say. Whatever expiry you set, tracking prevention in the major browsers can shorten or ignore it — particularly for cookies set by scripts rather than by your own server. So the number in the settings panel is a ceiling, not a promise, and it applies to some visitors and not others.
That is why an affiliate programme’s advertised cookie window is closer to a marketing figure than a technical guarantee. It describes their intent. The actual retention depends on the browser, the platform, and whether the visitor cleared anything in between.
If you need something durable, the answer is not a longer cookie. It is an identifier that does not depend on one — a click ID carried through the funnel, or a first-party record keyed to something the customer gave you.
Do not confuse with
Close enough to get mixed up, different enough that the mix-up costs something.
- Attribution window The period after an ad click or view during which a later conversion still counts for that ad. A conversion after the window closes goes to another source.
- Click ID A unique value an ad platform adds to the landing page URL on each click, such as Google's gclid or Meta's fbclid, so a later conversion can be matched to it.
- Consent mode A setting that passes each visitor's consent choice to your tags, so they change what they send. Google Consent Mode is the most common example.
- Tracking prevention Browser features that shorten how long identifiers last and block some tracking requests. Safari's Intelligent Tracking Prevention is the best-known example.