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Cookies work on the server. Cookies and Similar Technologies Policy. What are cookies

Almost every Windows user has encountered the concept of cookies. What they are, why they are needed and why it is advisable to clean them, read within the framework of this publication.

What are cookies

Cookies are text file with data that is recorded in the browser by the server of the site you visit. These data are:

login and password information;
individual settings and user preferences;
visit statistics, etc.

Using this data, the site you visited will be able to identify you. This happens as follows:

the site server queries the browser for information in the cookie file;
the browser provides this information by sending a response to the server;
Depending on what information the site server receives, you will be identified or become a new person for the site (if the cookies are cleared).

The main parameter of a cookie is its expiration date. By default, this is one computer session. Files are deleted when the browser is closed. If they have an expiration date, they become permanent and are deleted upon expiration or by the browser cleanup function.

What are they needed for?

First of all, they are needed for the convenience of using the Internet. For example, once you log into your profile on the site, you will not need to constantly enter your login and password after closing the tab.

Also, thanks to cookies, individual account settings are saved. For example, some sites offer to add to favorites, change the design, change the interface using such files with an expiration date.

Where are cookies stored?

Files are saved in a custom folder. Each browser has its own path:

Opera C:\Users\Username\AppData\Local\Opera Software\Opera
Google Chrome C:\Users\Username\AppData\Local\Chromium
Yandex.Browser C:\Users\User_Name\AppData\Local\Yandex\YandexBrowser
Mozilla Firefox C:\Users\Username\AppData\Local\Mozilla\Firefox

Why clean?

It is advisable to clear your cookies from time to time. In addition to being useful, they can also cause some inconvenience:

They provide quick access to your profiles without entering a login and password. If a stranger is at your computer, he will be able to access your personal data.
In addition, if an unauthorized person ends up on your computer, you can track your browsing history using the uncleaned cookies. This is bad from a privacy perspective.
If the site processes your cookie file incorrectly, you may not be able to log into your profile, or some functions on the web service will not work correctly.

How to clear cookies?

Here's an example of cleaning for popular browsers:

Opera. Ctrl+H → Clear history → Cookies and other data from sites.
Google Chrome. Ctrl+H → Clear history → Cookies, as well as other data from sites and plugins.
Yandex browser. Ctrl+H → Clear history → Cookies and other data from sites and modules.
Mozilla Firefox. Ctrl+Shift+Del → Cookies.

How to disable?

In general, the creation of cookies can be disabled in your browser. This feature is available in all popular browsers, so there shouldn't be any problems. But after turning off this function, some sites may stop working, since they interact with the user exclusively using cookies.

To disable in popular browsers:

Advice! If you see notifications in your browser: “cookies must be allowed” or “an attempt to save a cookie is blocked,” then your browser does not save cookies by default. Open settings and enable saving cookies.

Hello, dear readers of the blog site. Almost immediately, any novice Internet user is faced with the concept of cookies. What does this mysterious word mean? Why are they sometimes cleaned? How do third-party cookies differ from direct cookies? How to turn them on or off? And most importantly - why?

No, we, of course, at the subconscious level understand that this is a necessary thing, since everyone is talking about it, but still it would be nice to dig a little deeper in order to separate truth from fiction and dispel some of the myths associated with these mysterious cookies. Well, and at the same time understand their purpose in order to clean, enable and configure their reception in the browser with skill.

What are cookies - myths and reality

If we talk in simple language, then cookies are just pieces of data exchanged between your browser and the web servers that host the sites you visit (). The fact is that the http protocol is designed in such a way that every time you access a new page of the same site, your browser seems to get acquainted with the server again and everything that you did on the site’s pages a little earlier will be completely forgotten.

It would seem, so what... However, most sites will not be able to work without such a thing as cookies. More precisely, they can, but they will lose some of their functionality.

For example, if working on a website requires authorization, then every time you go to a new page you will have to do the following:

The user enters a name and password into the login form located on the site and sends them to the server.
The server receives them and checks them for correctness, after which it returns the page requested by the user to the browser. But along with its code, the browser receives a cookie with a session identifier. As a rule, they will be stored in the browser for some time, during which the user will be able to work with the site without re-authorization.
When requesting other pages of the site from the server, the browser, along with the request code, also sends a cookie with a session identifier. The server checks the identifier against its database and, under favorable circumstances, returns the code of the requested page.

And in the online store you won’t be able to buy anything at all, because without cookies it won’t work "virtual shopping cart" for storing purchases.

What is noteworthy is that the development of the cookie standard began precisely for the implementation of a shopping cart in a package intended for online commerce. This happened in the early nineties of the last century by the authors of the now forgotten Netscape browser. The standard was then revised to try to limit the use of cookies to collect personal data about browser users.

Cookies can also be used to store settings that the user has made on the site. For example, you can set the number of answers that will be shown and the size of snippets. This data will be stored in your browser and applied every time you make a search.

In general, cookies are necessary and useful in most cases. But controversy still rages over the fact that third-party Cookies pose a threat to user privacy. Where do these third-party cookies come from and what are they? The fact is that when loading (rendering) a web page, data can be loaded not only from the server where the site is actually located, but also from third-party servers.

Examples of such things can be visitor counters, scripts for loading contextual advertising blocks, and various images stored not on the main site. And all this wealth, when downloaded, can transfer its own cookies to the browser, which in this case will be called third-party. It is they who are usually feared in terms of privacy violations.

However, in the settings of some browsers Loading of third-party cookies can be allowed, because by default it is blocked for security reasons. In this regard, in various Internet browsers you can find approximately the following set of options:

Completely disable cookies.
Clear all cookies when exiting the browser.
Prohibition or restriction on the use of third-party cookies
Creating a “white” and/or “black” list of sites from which cookies will either be allowed or blocked.
Some browsers even have a manager to clear these records for individual sites.
Setting limited expiration times for cookies.

Regarding the last point. The fact is that there are cookie records that are deleted themselves when your session with a particular site ends. However, site developers have the opportunity to specify the lifetime of these records, after which they will be cleared. Such cookies are called persistent and it is precisely the limitation of their lifespan that is discussed in the last paragraph. They are usually stored in a separate file, which may be called cookies.txt.

Now let's dispel a few myths with which cookies have become overgrown:

Cookies do not identify a specific person (you), but individual browsers. Having opened a page of the same site in another browser, you will be asked to log in again, because there will be no cookies indicating that you were previously logged into this browser. If several people use the browser, then again this technology will not differentiate between them.
Cookies are not programs (they are ordinary text fragments), so they cannot be sources of infection of your computers with viruses, and they themselves cannot be viruses.
They also have nothing to do with windows popping up spontaneously in the browser. These things are disabled in various browser settings.

Now let's list what is really cookies can do:

They can be used to track which pages you visited, and the retention period for this data can be quite long. The intelligence services of the world's most democratic country were once accused of using cookies to spy on them and obtain sensitive data in this way.
If the traffic transmitted from your computer to the Internet is not encrypted, then attackers can intercept it and, among other things, read the cookie (intercept or replace it). This most often happens when using WiFi without encryption.
Cookies can also be set by programs in languages such as JavaScript, embedded in the text of pages, or other scripts running in the browser (i.e., without receiving this data from the server).
At the moment, this technology has alternative solutions, but cookies still remain the best option based on the totality of their capabilities.

How to clear, enable or disable cookies?

There are times when you need to clear cookies left by you after an Internet session. For example, if you logged in to some sites, but at the same time worked from someone else's computer(at a party, at work, in an Internet cafe, etc.). If you leave cookies, then another user may well log into the same site and get into your account without meaning to.

By the way, on many sites now, when entering your login and password, you can check the “Someone else’s computer” checkbox so that authorization information is not saved in cookies. Well, also, all modern browsers have an “Incognito” mode or private travel on the Internet, when no traces of your presence remain on the computer.

In addition, cookies may need to be cleared if problems occur. problem opening any pages. Of course, the first step will be, but if this does not help, then you will have to go further and follow the steps described below.

In (before version 12.16), you need to select “Settings” - “General settings” from the top menu of the “Opera” button. In the window that opens, go to the “Advanced” tab, and then select “ cookie».
Here you can enable or disable the acceptance of cookies in general or only from the site you are visiting (i.e., third-party records will not be accepted). There is also a manager that will allow you to delete or change cookie records for each of the sites you visit separately.
If you want to just clear cookies, then select “Settings” - “Delete personal data” from the top menu of Opera, and on the tab that opens you can clear either all cookies or only those received in the last browser session:
IN new Opera(with a version number higher than 12.16) you will need to select “Other tools” - “Clear browsing history” from the “Opera” button menu:
On the tab that opens, just check the “Delete cookies and other site data” box and click on the “Clear” button located below:
In and just press the keyboard shortcut Ctrl+Shift+Delete, then in the window that opens, check the “Delete cookies and other site data” box and click on the “Clear history” button located below.
Yes, you can also select the period of time for which cookies will be cleared using the method described above.
You will need to press the key combination Ctrl+Shift+Delete, or select “Journal” - “Delete recent history” from the top menu of the “Firefox” button.
In the window that opens, just check the box “ Cookies", select the period for which they need to be cleaned, and click on the "Delete now" button.
To clear cookies, you can press the key combination we are already familiar with: Ctrl+Shift+Delete.
Then you need to check the “Cookies” line and click on the “Delete” button located below.

Good luck to you! See you soon on the pages of the blog site

2. Programming Cookies

Setting Cookies

Now you can start programming Cookies. To set Cookies, use the SetCookie function. In general, you can specify as many as six parameters for this function, but only one of them is required - pathe:

name - specifies the name (string) assigned to the Cookie.

value - defines the value of the variable (string).

expire - variable lifetime (integer). If this parameter is not specified, the Cookie will “live” until the end of the session, that is, until the browser is closed. If a time is specified, then when it arrives, the Cookie will self-destruct.

path - path to Cookie (string).

domain - domain (string). The value is set to the name of the host from which it was installed.

secure - transfer via HTTPS connection.

Usually only the first three parameters are used. Listing 4 shows some examples of setting Cookies.

Listing 4. Examples of setting Cookies

/./ Until the end of the session

SetCookie("Test","Value");

.// Lifetime - one hour after installation

SetCookie("My_cookie", "One hour",time()+3600); ?>

When using Cookies, you need to keep in mind that Cookies must be set before the first script output (either an echo statement or the output of some function). Therefore, it is advisable to set Cookies at the very beginning of the script. The thing is that Cookies are set using a specific server header, and if you output anything, that means the body of the document begins. As a result, Cookies will not be installed. Here's what you get if you set Cookies

not possible: Warning: Cannot add header information - headers already sent by (output started at /var/www/html/cookie.php: 2) in /var/www/ html/cookie.php on line 4

Reading Cookies Values

Accessing Cookies is quite easy. All of them are stored in the environment variable HTTP_COOC1E. If we have installed several Cookies, then in the HTTP_COOC1E variable they will be listed separated by “;” (separated by semicolons). For example: mycookie=valuel;mycookie2=value2.

To read the value of Cookies, you can access them like ordinary variables. For example: echo $Test ; Just remember to check the existence of the variable. In conclusion, I will give an example of an “individual counter” of visits. The script code is shown in Listing 5.

Listing 5. Custom counter using Cookies

// If the variable does not exist, declare it if (! isset(51na Counter); $lnd Counter = 0;

// Increase the counter

/* Set a Cookie that will live until reinstallation Windows user, that is, for a very long time. If you are interested, the browser will delete it 07/18,-"2 9 08:49 */

SetCookie("Jnd_Counter", $I na_Counter, Ox6FFFFFFF) ; echo "You have visited this site $Ind_Counter times"

I said above that you cannot use the echo statement before setting Cookies. I just made a similar mistake myself. If there is no echo statement and your program does not have one (at least before calling SetCookie() ), and Cookies cannot be set, make sure that the program start marker characters are -

Home of the site

Naturally, I didn’t see the \n character, and PHP “thought” that it was a fragment of an HTML document. As a result, Cookies were not installed, since Cookies are installed when the document header is generated, and after the first output of the script, header generation stops.

You've probably come across the term cookies while using the Internet. What it is? Essentially, cookies are a file or several small files that store text information. They are created when you visit sites that support this technology.

How do cookies work?

Everything is very simple. As soon as the browser receives a specific web page from the site, the connection between it and your PC is severed. If you decide to go to another page of the same resource or update the current one, a new connection will be established. On sites where there is no user authorization, this does not create any problems. But if it is necessary, without additional measures the resource is not able to “remember” the people visiting it and display information in accordance with the preferences of each of them. Cookies help to avoid a situation in which, when moving between different pages of a site, a person is not perceived by the service as a new, unauthorized visitor. You already know that this is text information. And cookies work very simply: when you move from one page to another, the server sends a request to the computer for the data from the cookies. Using them, he finds out who is going to perform such an action, and then, based on the information received, he grants or denies the request. Cookies are also used when creating online stores. It is thanks to them that the familiar shopping cart can exist, in which data about selected but not yet purchased goods can exist. And it is cookies that allow the specified products not to disappear from it while you are browsing other parts of the catalog and placing an order.

How are cookies useful?

You already know about several aspects of using cookies. We also managed to find out what it is. Now let’s talk about how else this technology can be useful and in what cases you can’t do without it.

Surely you know that now many services have so-called “affiliate programs”. Almost all of them are long-term and last for months or even years. Throughout this period, information is stored on the hard drive, thanks to which the partner will receive his percentage if the user who follows his link orders a service or product from the seller.

When working with visit counters, rating and voting systems, cookies are also used. What does this give in this case? Cookies are necessary so that the system can determine that a given user has already followed a link or left his vote. That is, there is some kind of insurance against artificial markups. There are ways to bypass such protection, but for ordinary users this result is more than enough.

What should you be wary of?

When working with cookies, it is important to remember that in some cases, seemingly harmless text information can be dangerous.

Cookies are one of the most important potential causes of online privacy violations. Why is this happening? Advertising sites always track which advertisements a particular user views. Cookies store data about which advertisements a person has already seen and track which topics are of interest to him. And while we are talking about cookies for a single site, there is no need to talk about the leakage of personal information. But if we are talking about large advertising networks, the codes of which are present on the vast majority of resources, everything becomes more complicated. Thus, thanks to the system, it can collect almost all the information about a person’s online activities. And if he enters his first and last name on some website, it becomes possible to connect all these actions with a real person.

There are other problems associated with cookies. They are mostly encountered by programmers who write document code. cookies for different sites. Without first reading professional sources, you can allow logins and passwords for the site to be stored in cookies. As a result, it becomes very easy to seize them and use them for your own purposes. However, almost all more or less serious sites store passwords and logins in a database on the server. Cookies are used here simply as a conditional identifier for the user. Moreover, it is issued only for a short period of time. That is, even if a hacker manages to gain access to cookies, he will not find any valuable information there.

How to enable, disable and clear cookies?

If you decide to disable cookies, please note that you will have to re-enable them each time you visit a site that requires them.

For Mozilla Firefox. Go to “Tools”. Next, you should find the “Settings” item, and in it - the “Privacy” tab. Opposite Firefox, in the “History” frame, you need to select “do not remember” from the list.

For Google Chrome. Open “Options” by clicking on the button in the form. After that, go to “Advanced” -> “Content Settings”. In the window that appears, you need to select Cookie, and then check the box that prohibits sites from storing data.

As you can see, disabling or re-enabling cookies in Chrome and Mozilla Firefox, the most popular browsers, is very simple. In other browsers, this is done in the same way, using the “Security”, “Privacy”, etc. tabs.

If you need to clear cookies, it is faster and easier to do this not using standard browser tools, but using a special utility - cCleaner. Before cleaning, you need to close all browsers, otherwise you will not be able to delete all cookies.

In general, the best option is to install one of the programs that automates work with cookies. Nowadays there are a huge number of such applications, they weigh quite a lot and relieve users from the need to constantly change parameters manually.

Cookie(cookies, cookies) is a small amount of named data (in text form) stored by the browser and associated with a specific WEB page or WEB site. Cookies act as a web browser's memory so that server-side scripts and programs on one page can work with data entered on another page, or so that the browser can remember user preferences or other state variables when it returns to a page it previously visited. Cookies were originally intended for server-side script development and are implemented at a low level as a protocol extension. Cookie data is automatically passed between the web browser and the web server so that server-side scripts can read and write cookie values stored on the client side.

Cookies are described in RFC 2965. Cookies are designed to store small amounts of data occasionally. They are not a universal means of communication or transmission of data, so moderation should be exercised when using them. The RFC 2965 specifications recommend that browser manufacturers do not limit the number and size of cookies that can be stored. However, restrictions can exist:

There can be no more than 300 cookies in total (300 name-value pairs). If the limit is exceeded, the oldest files are overwritten.

The size of one cookie cannot exceed 4kb. If exceeded, the oldest bytes are overwritten.

No more than 20 cookies can be installed from one domain (second level, including subdomains).

For a specific site, only those cookies that were installed by it will be available.

Cookie attributes

Cookie attributes: expire, max age, path, domain and secure.

In addition to the required name and value, each cookie has several optional attributes that control its lifetime, visibility, and security.

expire- by default, cookies are temporary (session) - their values are saved for the duration of the Web browser session and are lost when the user closes the session. In order for a cookie to persist after the end of a session, you need to tell the browser how long it should be retained. Initially, the expire attribute was used for this, indicating the expiration date of the cookie. The expire value (RFC 2616) is written in the format "Wdy, DD Mon YYYY HH:MM:SS GMT". If this attribute is not set, the cookie is stored for one session, until the browser is closed.

max age- similar to the expires attribute, but the retention period is specified in seconds (RFC 6265). The decimal value is not a negative integer. After the specified time has elapsed, the client must reject the cookie. A value of zero means the cookie should be rejected immediately.

Setting the value of any of these attributes (expires, max age) causes the browser to store the cookie in a local file so that it can be read the next time the user visits the web page. Once the expiration date is reached or the max age period has expired, the browser will automatically delete the cookie.

path- specifies the web pages with which the cookie is associated. By default, a cookie is associated with the web page that created it and is available to that same page, as well as any other page in the same directory or any of its subdirectories. If, for example, the web page http://www.example.com/catalog/index.html creates a cookie, then this cookie will also be visible to the pages http://www.example.com/catalog/order.html and http:/ /www.example.com/catalog/widgets/index.html, but we do not see the page http://www.example.com/about.html. This default visibility rule is usually sufficient. However, sometimes cookie values need to be used throughout a multi-page website, regardless of which page created the cookie. To do this, the cookie is set to path(path=/;). Then any page on the same web server that contains the specified value in its URL will be able to use the cookie.

domain- by default, cookies are available only to pages loaded from the web server that installed them. However, large websites may need to be able to share cookies across multiple web servers. If the domain attribute for the cookie is not set, the default value will be the name of the web server on which the page is located. Please note that you cannot set a cookie's domain to be different from your server's domain.

secure is a Boolean attribute named secure that determines how cookie values are transmitted over the network. By default, the cookie is not protected, i.e. it is transmitted over a regular unsecured HTTP connection. However, if the cookie is marked as secure, it is sent only when the exchange between the browser and the server is organized via the HTTPS protocol or other secure protocol. Defaults to false.

Cookies are defined by a triple of parameters name-domain-path. That is, cookies with different paths or domains are different cookies, even if they have the same names. Accordingly, the cookie is changed to a new one only if the new cookie has the same name, path and domain. In other cases, new cookie values are added to the old ones.

Cookies can be installed in a browser (or other program) in two ways:

using the protocol Methods and structure of the HTTP protocol, which provides two parameters (headers) Set-Cookie (the server indicates to accept the cookie) and Cookie (browser response). In addition to the name/value pair (name=newvalue), a cookie can contain an expiration date, path, and domain name. These attributes must come after the name=newvalue pair and are separated by a semicolon. For example:

Set-Cookie: name=newvalue; expires=date; path=/; domain=.example.com. or Set-Cookie: RMID=732423sdfs73242; expires=Fri, 31 Dec 2010 23:59:59 GMT; path=/; domain=.example.net

The domain and path tells the browser that the cookie should be sent back to the server when URL requests are made for the specified domain and path. If they are not specified, the domain and path of the requested page are used.

cookies (HTTP and/or PHP)

setcookie- the cookie value is URL encoded before being sent to the client. When received back, the cookie value is decoded and placed into a variable with the same name as the cookie name. If you don't want the values to be encoded, use the setrawcookie() function

setrawcookie- sends a cookie without converting the value, otherwise completely similar to the setcookie function

Cookies are part of the HTTP header methods and structure, so setcookie() must be called before any output to the browser. This is the same limitation that the function has header(). You can use output buffering functions to delay the output of a script until you know whether cookies or other headers need to be set.

Any cookies sent to the server by the client's browser will be automatically included in the $_COOKIE superglobal array if the variables_order directive contains the letter "C".

When the browser sends a cookie back to the server, it only sends the value. It is not possible to access the domain, path, expiration time, or security status of a cookie through the $_COOKIE array because the browser does not send it to the server.

Installation. Easy setup SetCookie("Name","Value")

Arrays of cookies.

Setcookie("mycookie1["id"]", "value_id"); setcookie("mycookie1["lang"]", "value_lang");

The cookie value is not available in the $_COOKIE array within the same request in which the cookie is set. In other words, the setcookie() function does not change the value of the $_COOKIE array. However, for all subsequent requests, each previously set cookie is placed in the $_COOKIE array.

To assign multiple values to a single cookie, append to its name. For example: setcookie("MyCookie", "Test", time()+3600);

On success, setcookie() returns TRUE. However, this does not mean that the client application (for example, a browser) correctly accepted and processed the cookie. That is, it is NOT possible to determine from the behavior of the setcookie function whether cookies are enabled in the client’s browser.

Reading. if (isset($_COOKIE["lang"])) ( print "Cook".$_COOKIE["lang"]." exists."; )

To print the names and values of all cookies sent in the current request, loop through the $_COOKIE array:

Foreach ($_COOKIE as $cookie_name => $cookie_value) ( print "$cookie_name = $cookie_value
"; }

Change. If a cookie takes on a new value when there is already a cookie in the browser with matching name, domain and path parameters, then the old value is replaced with the new one. In other cases, new cookie values are added to the old ones.

Removal. You only need to specify the name of the cookie, for example SetCookie("Name"). This will delete the installed cookie named "Name" - this is the official recommendation for deleting cookies.

A working example of deleting and setting cookies using PHP: "; ) else ( setcookie("my_cook", "My name is John", time() + 60 * 60 * 24); echo "Cookie set to user." . "
"; ) var_dump($_COOKIE); ?>

Unclear Cookies: _utma, _utmb, _utmc, and _utmz

Sometimes, when checking installed Cookies, you can see variables with strange names: _utma, _utmb, _utmc. These cookies are set by Google Analytics. A quick introduction to Google Analytics Cookie Variables

Utma – issued upon your first visit to the site.

Utmb – variable tracks the time of visiting the site. Each time you visit a page, it marks a “transition”. The default lifetime is 30 minutes.

Utmc – tracks when the user closes the browser. If there is no cookie when you log in again, a new visit is counted, regardless of _utmb

Utmv – variable used to set “own” user variable

Utmx – variable needed for Website Optimizer. The lifetime of the _utmx cookie is 2 years.

More information about variables can be found in the Google Analytics documentation.

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