Why do browsers use cookies, strong caching of browser caches

It is convenient for the next Internet browsing, and offline browsing of the web, and you can make the browsed web page open faster.

The browser's cache is divided into strong cache and negotiation cache.

1. When the browser loads the resource, it first followsSome http headers for this resourceDetermine whether it hits a strong cache, and if it does, the browser reads the resource directly from its own cacheNo requests are sent to the server。For example, if the browser loads the web page where it is located, and the cache configuration of the CSS file hits the strong cache, the browser will load the CSS directly from the cache, and the request will not even be sent to the server where the web page is located.

2. When the strong cache is not hitThe browser will always send a request to the server, and the server will verify that the resource has hit the negotiation cache against some other HTTP header of the resourceIf the negotiation cache hits, the server will return the request, but instead of returning the data of the resource, it tells the client to load the resource directly from the cache, and the browser will load the resource from its own cache. The common denominator between a strong cache and a negotiated cache is that if it hits, it loads resources from the client cache, not from the server; The differences are:

The strong cache does not send requests to the server, but the negotiation cache sends requests to the server.

3. When the negotiation cache is not hit, the browser loads the resource data directly from the server.

Here's just a look at the implementation of strong caching:

Strong caching is implemented using two HTTP response headers, expires or cache-control, which are used to indicate the expiration date of resources in the client-side cache.

expires is an older strong cache management header, because it is an absolute time returned by the server, when the server time and the client time are quite different, the cache management is prone to problems, such as arbitrarily modifying the client time, which can affect the cache hit result. So at that time, a new header was proposed, which is cache-control, which is a relative time, when configuring the cache, in seconds, expressed as a numeric value, such as: cache-control:

max-age=315360000

These two headers can be enabled only one or both, and when both expires and cache-control exist in the response header, cache-control takes precedence over expires:

What are the effects of too much browser caching? Let's take a look today.

1. For browsers, too much browser cache will cause the browser page to load slowly, or the incomplete display page will be unresponsive, or even the browser will crash and close the browser automatically;

2. It will occupy the memory of the mobile phone or computer, the memory of the mobile phone or computer is limited, if the cache of the browser occupies too much memory, other software or applications will not have enough memory to open and use, even if it can be opened and used, it will be very slow, resulting in Caton, etc.

Extended tip: How to clear your browser cache

We often use browsers to browse the web in life, ****, etc., in the process of making the stupid world will leave a lot of Internet traces and cache records, which need to be cleaned up regularly, and the operation of cleaning up browser caches on computers and mobile phones is different:

1. How to clear the browser cache on the computer.

1) Open the browser, click the "Settings" icon in the upper right corner to enter the settings option.

2) In the settings interface, find "Clear Browsing Data" or "Clear Chuntuan Browsing History".

3) Check the content to be cleaned and the time range for cleaning, and after confirmation, click Clear.

2. How to clear the browser cache on your phone.

1) Open your phone's browser, click on the settings interface below, find "Clear Data", and click on it.

2) Select the cache you want to clean in the pop-up interface, click "Clear", and wait for a while before the clearing is successful.