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Monday, November 17, 2014

Clearing Cache, Cookies, And Other Website Data

Most of us, as we surf the Internet, are going to surf some websites, repeatedly.

Everybody has favourite websites. When we surf the same website, over and over, some of what we do and see may not change a lot.

To keep us from wasting our time, and generating unnecessary network traffic, our browsers keep track of the websites that we visit over and over, save records of what we do and copies of what we see, and note what has changed. The website content, stored locally, is known as "private" data.

There are times when we need to clear "private" data. Note the different browsers - and the different menus and selections, provided by each browser.

  • If you have a problem when viewing your blog - or if you wish to immediately refresh your personal view of your blog, you should clear "cache".
  • If you have a problem maintaining or publishing your blog - maybe when switching between Draft and Production Blogger, you should clear "cookies".
  • Whenever you clear cookies, you should clear cache, also - so, if you have a problem when maintaining or publishing your blog, you should clear "cache, cookies, and sessions".

There are other reasons for clearing private data - but there are also reasons for not clearing private data, indiscriminately. It will be worth your time, to understand what and when you should clear - and not clear.

Normally, you would not, routinely, clear private data.

What if you use a publicly shared computer - maybe in a coffee shop or library? Or maybe, you carry your computer to a coffee shop or library? Do you want your private details - such as account names, passwords, even a list of what websites you surf - being available for other patrons of the coffee shop or library, after you leave?

Most of us do not want our private details, visible to any curious fellow patron - or maybe to our family either. But not all data is equally as damaging, if revealed to strangers, or to people who know us.

To help us keep our private lives private - yet not waste time or generate unnecessary network traffic, our browsers offer us the opportunity to save some content, and to delete other content - when we know what options are available to us.



Cache is simply locally stored copies of code and static pages, that you and other people, using the computer, might accumulate. Cache contains no sensitive, personally identifying material - other than (again) possibly identifying what websites you have visited.

If you share a computer with another person, identifying what websites you visited, and what websites the other person visited, will require knowing times each of you used the computer. There are no personal identifiers which indicate which of you visited a given website.

Forms contain online entered data, such as account names. Forms are slightly less sensitive than passwords, since they may contain large volumes of random data. Look at the boxes in the Blogger dashboard - those are all forms. Hidden in the forms, you may find an account name - or an email address. It's like asking how dangerous a needle may be, in a stack of hay.

History is a log, describing what websites, and website pages, that you have visited. History might be important if having people, other than you, know that you visit certain websites; other than the personal embarrassment possibility, history is relatively harmless.

Passwords are the most sensitive bit of data, that you can store on your computer. Someone extracting your passwords, on a per website basis, can use your account in each website, to operate as you. An online password is just as sensitive as the password (aka "PIN") that you might enter at an ATM.

Preference cookies (aka "cookies") are local storage of website relevant details. Preference cookies are miscellaneous settings, used to remember choices which you might make, when viewing a given website, repeatedly. Some browsers identify "preference cookies", and "session cookies", collectively, as just "cookies". Firefox, in various places, identifies "preference cookies" as "cookies", and "session cookies" as "sessions".

Session cookies (aka "sessions") are a cookie, designated by some browsers, as containing login identifiers, and other data relative to one website visit (but let you extend one "visit" to include multiple browser openings and closings). Firefox designates the Blogger login cookie as a session cookie. This is why, when I advise you to clear Blogger dashboard problems, I always specify clear "cache, cookies, and sessions".

In order of sensitivity, I would rank the above elements in a different order.

  • Passwords.
  • Forms.
  • Session cookies.
  • Preference cookies.
  • History.
  • Cache.

Look at cache, to start. Cache is locally stored copies of content, from remote servers. Other than inadvertently revealing our favourite naughty content, there is no danger in cache content being seen to other people. There are three scenarios, when we might want to clear cache.

  • To clean up the computer, when it is running slower than normal.
  • To provide an up to date copy of a website, immediately.
  • When investigating a website login problem, such as a Blogger dashboard problem, which requires clearing cookies.

Cache takes up thousands as much space as cookies, and as passwords.

At the other end of the sensitivity scale, you find Passwords. My personal advice is to not store passwords, period. If you want convenience when accessing a website like Blogger, which offers long term login sessions - when you use a private and safe computer - simply don't log out, from Blogger. If you never clear session cookies, you never have to log out.

If you enjoy the convenience of online banking, on the other hand, you should always log out after an online banking session. If you never store passwords, for online banking, you never have to worry about clearing passwords.

In the middle of the scale, we find Cookies. A cookie is a small, encrypted file, which contains a single setting that lets us visit the same website repeatedly, without having to re enter something.

The Google login cookie (aka "session" cookie) lets us visit Google (and Blogger), and maintain our blogs, without having to login, over and over. This is the infamous "third party" cookie which we need, to use Blogger readily.

Cookies, since some provide login data, are encrypted. Open a cookie file, using a text reader, and see what is there (But do not use "Save" to close the text reader), if you wish to understand.

If you have a problem when viewing your blog - or if you wish to immediately refresh your personal view of your blog, you might clear "cache". If you have a problem with your Blogger dashboard - maybe when switching between Draft and Production Blogger, on the other hand, you would want to clear "cookies". Whenever you clear cookies, you should clear cache, also - so, if you have a problem when maintaining or publishing your blog, you will be advised to clear "cache, cookies, and sessions".

If you have inconsistent private data (cookies don't properly match cache or scripts), you may have to deal with one of the mysterious bX codes. When this happens, then clearing "cache, cookies, and sessions" may be one of the first things to try.

Note that not all problems involving "cache" or "cache, cookies, and sessions" may be solved by "clearing cache" or even "clearing cache, cookies, and sessions". Some problems may require corrected filtering. Also, not all problems, that involve cache, can be necessarily solved by clearing browser cache.

All of these are personal preferences, which I exercise - when using my own personal computer, in the privacy of my home. Other people may be more strict - or some computer owners may never clear anything. When using your computer outside your home - or maybe, when using a public computer - you may wish to be more careful.

My personal advice, for using a public computer, is simple.

  • Never, except in an absolute emergency, use a public computer for online banking.
  • Whenever finishing a session on a public computer, always clear all private data, and restart the computer.

Some short term use public computers, such as stand up terminals in libraries and shopping centres, are specially designed to reload the entire system configuration, and operating system, and wipe all "private" data, after each individual person has used the computer. If you must use a public computer, those would be the safest ones to use.

Similarly, if you carry your own computer outside your home, you may be concerned with other people seeing what's on your computer, intercepting your network activities (if you use a public network), and / or stealing the computer. Depending upon which possibility concerns you, you might take any or all precautions, before carrying the computer out the door.

  • Clear passwords (if you store passwords, locally).
  • Clear history and cache (if you fear people browsing your computer).
  • Clear all private data (if you fear theft).

Who knows what embarrassment (financial, and personal) you might save yourself, by thinking ahead?

Dude, hit me with a comment!

Angelina Lenahan said...

A while ago, you provided a how-to clear cookies, cache, history for various browsers. I copied info for my browser, which has two ways to clear above: I can choose the way you advised, or I can choose to select the option of clearing every time I log out. I have FF 3.3, so what do you recommend? I have no PID on my PC, no banking info, etc. Since following your advice, loading pages take nanoseconds; everything runs great. Thanks.

Chuck Croll said...

Angelina,

Do you have FF V3.3 - or FF V33?

Angelina Lenahan said...

33. Was there a 3.3? While we are on the subject of 33, FF keeps asking me to update to the 34...what say you?

Angelina

Chuck Croll said...

You typed "3.3" above - scared me. 8-P

I think FireFox has proven their ability to deliver stable updates. I'd go with whatever they come up with.

Angelina Lenahan said...

chuck, we got off the subject when you asked what v of FF i had. what i wanted to know was do i manually clear c,c&hx or let FF do this when i log off automatically? can i depend on it each time i log off? thanks.

Chuck Croll said...

Angelina,

You can manually clear cache, cookies, and sessions - or you can have them automatically cleared, when you close the browser.

I don't see any benefit to have everything cleared, each time you close the browser. It's good to have stuff cached, across browser sessions. One day, you may have an experience, where you find out why I believe this.

I am working on an article about "browser sessions vs login sessions", and I may address your question in some detail.

But, it's your computer.