Set html cache

With the development of the Internet, the number of visits to the website is increasing, and the time required for users to access the website is getting shorter and shorter, which puts higher requirements on the performance and speed of the website. One way to achieve performance optimization is to set up HTML caching. This article will introduce what HTML caching is, why caching is needed, and how to set up HTML caching.

1. What is HTML caching

HTML caching is to store web page content in the cache of the user's browser and control whether the user needs to re-obtain the web page content instead of fetching it from the Web every time Obtained from the server. In other words, when a user visits a web page for the first time, the web server will transfer its content to the user's browser. When the user visits the page again, the browser will check the cache. If a copy of the page exists, the browser will directly copy it from Get the page content from the cache instead of sending a request to the web server again.

2. Why HTML caching is needed

1. Improving website performance and speed

Caching is undoubtedly an effective performance optimization method, which reduces the amount of time passed through the network How often the data is fetched so the page loads faster.

2. Reduce the load on the server

When the web server handles multiple user requests, enabling caching allows the server to save a lot of resources, thus reducing the load on the server and improving the website scalability.

3. Reduce the use of network bandwidth

After enabling cache, you can reduce the number of data transmissions and reduce the use of network bandwidth, so you can better cope with a large number of accesses Condition.

3. How to set up HTML cache

When setting up the cache, you need to add the cache control field to the HTTP response header. The following HTTP response headers are introduced in detail:

1. Expires

The Expires header tells the browser when the page will expire. This time should be an absolute date and time in the future, returned to the browser by the web server.

For example, the following statement sets a cache period of 1 hour:

Expires: Thu, 21 Sep 2023 19:20:39 GMT

2. Cache-Control

Cache-Control header to cache the entry The method provides cache management options for web servers, allowing control over how clients, proxy servers, and web servers cache pages, store them, and how long they will be cached.

For example, the following statement tells the browser that it can cache the request for three hours:

Cache-Control: max-age=10800

3. Last-Modified

Last-Modified is sent by the web server The HTTP response header is used to tell the browser the last modification time of the resources (documents, images, etc.) on the server. This time very simply tells the browser when your page or image or whatever should be removed from the cache.

For example:

Last-Modified: Thu, 12 Dec 2019 03: 15: 02 GMT

4. ETag

ETag is an HTTP response header sent by the web server to support the use of resources on the web server. Cache verification is performed when modifying. During the HTTP request, the browser will submit this ETag and tell the server the last modified version you have, which will allow the server to verify and return the only new version.

For example:

ETag: "1234abcd"

As a web developer, you need to pay attention to the following points:

1. Dynamic pages should not be cached.
2. You should not link the cache to a specific IP address because the cache will become invalid when the site is moved to another server.
3. Web servers should send HTTP response headers (HTTP response headers) to tell the browser when the cache expires.
4. Web pages involving encryption or security information should not be cached.

Generally speaking, HTML caching is an effective way to improve website performance and speed. We need to set appropriate caching rules according to actual needs to achieve the best results. At the same time, you need to be careful when setting up the cache to avoid security issues such as information leakage due to cache failure.

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