Hi.
My name is Maile Ohye.
I'm a senior support engineer at Google.
Have you ever wondered how websites remember your user
name and password every time you visit?
Or how online stores know which items you've added to
your shopping cart?
What makes these and other customized online experiences
possible are cookies.
So what is a cookie?
It's a small file that websites place
on visitors' browsers.
The information in the cookie file travels back and forth
between the browser it's stored on--
say Firefox or Internet Explorer--
and the websites the browser visits.
Let's say I'm visiting google.com for the first time.
Google places a cookie on my browser.
The next time I visit Google, whether it's seconds, days, or
weeks later, my browser automatically sends Google
that same cookie with a cookie ID number that allows Google
to recognize my computer.
All search engines and most websites use cookies.
Why?
Cookies allow the sites you visit to recognize your
computer when you return and then tailor your online
experience accordingly.
It's a lot like the claim check you get
from the dry cleaners.
When you come back for your clothes, the person working
there uses the number on your claim check to make sure they
give you the right stuff.
In the same way, when my cookie tells Google that I
visited its site before, Google is able to remember my
preferences, like the fact that I want to see my search
results in English, or that I've turned on SafeSearch, a
tool that blocks adult content from my search results.
What else do cookies do?
On weather sites they remember which cities you want the
forecast for.
On e-commerce sites they make sure all your selections are
in your virtual shopping cart when you go to check out.
And on finance sites they allow you to easily track your
stock portfolio without having to re-enter the information
every time you visit.
As you can see, cookies can save you a
lot of time and hassle.
And like a claim check, a cookie ID is usually just a
combination of letters and numbers.
Most of the time there's no personally identifiable
information in a cookie file.
No name, email address, or phone number.
And cookies cannot be used to run programs on your computer,
access information on your hard
drive, or deliver viruses.
But that's not the whole cookie story.
There are different types of cookies.
A first-party cookie is the kind of cookie I
just told you about.
A cookie that goes back and forth between your browser and
the website you're visiting, allowing that website to store
information about your preferences.
Third-party cookies work a bit differently.
Unlike first-party cookies that travel back and forth
between your browser and the website you're visiting,
third-party cookies typically travel between your browser
and the website of a company that's displaying an ad on the
site you're visiting.
That's why they're called third-party cookies.
Because the website sending cookies to your browser,
usually an ad-serving company, is actually a different site
from the one you're visiting.
Ad-serving companies use third-party cookies to
remember what ads have already appeared on your browser.
Like the fact that you clicked on an ad for a new Sony
Playstation game and saw the same Nintendo ad twice.
This information helps advertisers deliver ads that
are relevant to your interests, control the number
of times you see a given ad, and measure the effectiveness
of ad campaigns.
What if you don't want websites recording your
preferences or ad-serving companies knowing your web
browsing history?
Well it's easy to set up your browser to notify you when
cookies are sent, to refuse cookies from certain websites
or ad-serving companies, or to refuse cookies all together.
Choosing which cookies to refuse and which cookies to
accept is totally up to you.
Just remember that if you disable your cookies, websites
won't be able to retrieve your prior preferences or save
settings to customize your visits in the future.
I hope this gives you a better idea of how cookies help
Google improve your experience on our site, how other
websites and ad-serving companies use cookies, and how
you can control which cookies get sent to your browser.