Why cookies are invalid

The reason why the cookie is invalid may be that the cookie expires, the cookie is deleted, the cookie is overwritten, the cookie is disabled, the cookie path does not match, the cookie domain name does not match, security restrictions, etc. Detailed introduction: 1. Cookie expiration. Each cookie has an expiration time. Once this time is exceeded, the cookie will become invalid. When setting cookies, you can specify cookies by setting the "expires" or "max-age" attributes. wait.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

Cookie is a mechanism for storing data on the client side for tracking and identifying users in web applications. However, sometimes we may encounter situations where cookies are invalid. The following are some common reasons why cookies are invalid:

1. Cookie expiration: Each cookie has an expiration time. Once this time is exceeded, the cookie will become invalid. When setting a cookie, you can specify the expiration time of the cookie by setting the `expires` or `max-age` attributes. If the cookie expires, it will no longer be sent to the server by the browser, and the cookie cannot be used to identify the user.

2. Cookies are deleted: Users can delete cookies through browser settings or clearing browser cache. If the user clears the browser cache or manually deletes a specific cookie, the cookie will become invalid and can no longer be used.

3. Cookie is overwritten: When a website sets a cookie with the same name as another website, the latter will overwrite the former. In this case, the original cookie will become invalid and replaced by a new cookie.

4. Cookies are disabled: Some users may disable the cookie function of the browser or limit the use of cookies in the privacy settings. If the user disables cookies, the server cannot store and read cookies on the client, causing the cookies to be invalid.

5. Cookie path mismatch: Each cookie has a `path` attribute, which is used to specify the URL path that can access the cookie. If the `path` attribute is set, then only URLs matching the path can access the cookie. If the cookie's path does not match the current URL, the cookie is invalid.

6. Cookie domain name mismatch: Each cookie has a `domain` attribute, which is used to specify the domain name that can access the cookie. If the `domain` attribute is set, then only URLs matching the domain name can access the cookie. If the domain name of the cookie does not match the domain name of the current URL, the cookie is invalid.

7. Security restrictions: In some cases, browsers may restrict access to Cookies to protect user privacy and security. For example, if a website uses a secure connection (HTTPS) and a cookie is set over a non-secure connection (HTTP), the browser may consider this an insecure operation and block the use of the cookie.

In addition to the above reasons, there are some other factors that may cause cookies to be invalid, such as browser version, security policy, network proxy, etc. In order to ensure the validity of cookies, we need to pay attention to setting the expiration time, path and domain name of cookies, and follow the browser's security policy. At the same time, it is also necessary to consider the situation where users may disable cookies and provide other user identification and tracking mechanisms to ensure the normal operation of web applications.

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