This question is frequently asked. First of all, it should be said that there is no 90-day cookie in the technical sense and some things get mixed up on this topic. The following text attempts to explain the situation.
The 24-hour cookie (the real cookie!)
The only cookie that is generated when you click on an Amazon affiliate link is valid for 24 hours. This has the effect that the commission will be credited to you for all products that the user places in the shopping cart during this time and buys at the end. This also applies to products that you have not linked at all, e.g. if the user clicks your affiliate link to Sony’s PlayStation but chooses Microsoft’s Xbox within 24 hours and buys it, you will receive the commission for the purchase of the Xbox.
So where does the 90 day Amazon cookie myth come from?
The 89 days cart checkout extension (the unreal cookie!)
It can be explained by the fact that Amazon grants an extension of 89 days if the user has added a product to the shopping cart via your affiliate link but does not buy it directly. This mechanism of the Amazon shopping cart works automatically and does not need to be activated from the outside by any hotly advertised product with a magical function. This has nothing to do with a cookie.
A user clicks your Amazon affiliate link to the shop page of the PlayStation and places the product in the shopping cart. But he/she hesitates with the purchase and closes the browser. One week later the user clicks a third party Amazon affiliate link for a book and puts it in the shopping cart. Then the user completes the purchase of both products (PlayStation via your link, book via third party link). Due to the automatic 89 days cart checkout extension you get the commission for the PlayStation, not for the book.
You will receive the commission for products placed in the shopping cart via your link, as well as for other products added within 24 hours after clicking your link, as long as these products are purchased within the next 89 days.
That is the situation of the facts. This does not require any special technology, this is the case even with manually created Amazon affiliate links. Everything else is fairy tales or illegal methods.
There is no cookie for 90 days that works like the 24-hour cookie and assigns you commissions for all purchases made by a user over a period of three months just because he/she has clicked one of your affiliate links before. You just have to be able to add one and one together to realize that this is unrealistic. Anyone who promises this is not serious.