Washing Machine has special features for working with Cookies, those bits of information that web sites put on your computer to track your movements. You can see this in the Items list, where Cookies have a little text next to them that says Double-click to edit.
Double-click a cookie item; you'll see a window that looks like this:
At this point you can simply click Remove… to delete all Cookies from the selected domain. (As before, you can select multiple domains or multiple cookies by Shift-Clicking or Command-Clicking them.) Doing so means that your web browser will no longer remember your identity when you next visit that domain; the web site will no longer have access to your user name (if any), preferences you may have selected for that site, or your browsing history. This is useful if you want to clear your settings, such as if you accidentally chose to view a site in another language; however, some sites will require that you re-enter certain information, or view screens you've already seen before.
Many web sites feed you cookies from multiple sources, or domains, such as a domain they use to provide ads to the web site, or third-party companies that provide ads or other types of content. Determining which site set a particular cookie may be difficult.
You can view more detailed information about cookies, and, in some cases, edit that information. Clicking on the disclosure triangle to the left of a domain name gives you a list of the cookies associated with that domain. Click on one of those cookies to see which information it stores on your Mac.
You can change information stored in the cookie as long as the program to which it belongs (such as Firefox, Safari, etc.) isn't running. (If you try to edit a cookie while its program is running, Washing Machine will display a dialog box telling you to quit the application.) Most cookie information is stored in an obscure format that only the computer understands, so in most cases you're better off just deleting the cookie. But let's take a look anyway.
You can edit a cookie's Name, Path, and Value: simply click in the appropriate place and type the new information. Be aware that by changing a cookie's Name or Path (within the cookie file itself), the issuing domain probably won't be able to find it. That could be an alternative to deleting the cookie, if you want to render it powerless, yet still hold onto it for the future. If you do this, be sure you document your changes somewhere!
The Expires field shows how long the cookie will remain valid; you can change this by clicking in the area you want to change (such as the year or month) and then either typing in a new value or using the up- or down-arrow button to change it.
The Secure field tells whether the cookie was set via a secure protocol (HTTPS). There are certain other factors in making cookies "secure"; you cannot change this field with Washing Machine.
When you're done, click the Apply button to save your changes. (They won't be saved if you just click Done.) Or you can delete the specific Cookie at this point by clicking the Remove… button.
Let's say you want to clean every Cookie except for those that belong to a specific domain. (One example: you're using a work computer that needs certain Cookies to access your company's servers, but shouldn't store Cookies from other sites.) You can exempt specific domains from the cleaning process by choosing Washing Machine > Preferences… (or pressing Command-, ) then clicking on the Cookies icon.
To make sure Washing Machine doesn't clean the domains you want to keep, click Keep these domains. Then click the+ button and type in the domain name you want to keep. Add further domains by clicking the + button again, and remove unneeded ones by highlighting them and clicking the - button.