What is a Computer Cookie?
=== by Bob Sutherland ===
A cookie is a small file that the programming code of a website can create and save on your computer, tablet or cell phone. The cookie is saved among the files of your web browser software.
The programming code of a website can also search for and find a previously saved cookie among the files of your web browser software. If the previously saved cookie is found the programming code can read and/or modify the contents of the cookie.
If you have more than one user account on your computer, tablet or cell phone then a cookie can only be saved, read or modified in the user account you are using when you visit the website with the programming code that creates the cookie. A cookie cannot cross the boundary from one user account to another user account.
If you have a collection of different web browser programs on your computer, tablet or cell phone then a cookie can only be saved, read or modified among the files of the web browser program you are using when you visit the website with the programming code that creates the cookie. A cookie cannot cross the boundary from one web browser program to another web browser program.
There are many different web browser programs available. Some common ones are Opera (by Opera), Firefox (by Mozilla), Safari (by Apple), Chrome (by Google) and Internet Explorer (by Microsoft).
Here is what a typical cookie might look like according to my Opera web browser software. I looked at a long list of cookies on my computer and then typed this fake cookie to resemble their typical appearance.
File name: sntc
Created: Friday, April 1, 2016 at 9:58:45 PM
Expires: Saturday, April 1, 2017 at 9:58:45 PM
The file names of the list of cookies I looked at were usually short. I suspect that it is a requirement that the programming code on a website must already know what the file name is in advance before it can search for and find a previously saved cookie on your computer, tablet or cell phone. I may be wrong.
The content of the cookies I looked at could be anywhere from a single character to about a hundred or so characters long. Most averaged about twenty characters in length. The file content was always one continuous character string without any spaces. I do not know if there are any precise rules but it seemed that the file content may include capital letters, small letters, numbers, and some of the other characters on your keyboard. The file content was obviously a coded message that would only make sense to the programming code that created it.
The content of a cookie can be used to keep a record of the items you placed in your shopping cart or wish list when you visited an online store. Alternatively the content may be a unique identification number so a company (i.e. advertising agency) can recognize you and keep track of you whenever you visit websites with advertisements containing their programming code.
The domains of the cookies I found on my computer were obviously the websites of the owners or creators of the cookies. I recognized some of the domains as being websites that I had recently visited. I typed into the address bar of my web browser some of the domains I did not recognize and found they were websites of advertising agencies. The advertising agency probably had an advertisement posted on one of the web pages I had visited and that is how I wound up with one of their cookies.
The difference between the creation date and the expiry date of the list of cookies saved on my computer ranged anywhere from about two days up to two years. A one year time span seemed to be quite common.