Exploring HTTP Caching Mechanisms: Understand Common Caching Strategies

Decrypt HTTP caching mechanism: Do you know what common caching strategies are there?

HTTP caching mechanism is a very important part of web development, which can improve website performance and user experience. Caching allows users to load web content faster and reduces the load on the server. However, in order to use caching mechanisms correctly, we need to understand some of the common caching strategies.

1. Forced caching
   Forced caching means that when the browser requests a resource for the first time, the server will return the expiration time (Expires) and maximum cache time (Cache-Control) of the resource to the browser. server and tells the browser to use the cache directly during this period without having to send another request to the server. This can greatly reduce network latency and improve the loading speed of web pages. When the resource expires, the browser will send a request to the server again to obtain the latest resource.
2. Negotiation cache
   Negotiation cache means that when the browser requests a resource, the server will check the last modification time of the resource (Last-Modified) and the unique identifier of the resource (Etag), and store this information Returned to the browser together. When the browser requests the resource again, this information will be sent to the server in the request header. The server will use this information to determine whether the resource has been updated. If not, it will return a 304 status code to inform the browser that the cache can be used. Otherwise, a new resource will be returned.
3. Offline caching
   HTML5 provides an offline caching mechanism, which allows web pages to be accessed normally offline. By adding the manifest attribute to the header of the page and formulating a manifest file, the browser will cache all resources locally when the page is accessed for the first time. When the user is offline, the browser loads resources from the local cache, enabling offline access to web pages.
4. Shard cache
   Shard cache divides a resource into multiple fragments for caching, and only requests the missing fragments when requesting resources. This improves loading speed and reduces bandwidth consumption. For example, when loading a video, the video can be divided into multiple short segments for caching. When the user plays the video, only the missing segments need to be downloaded, which improves the smoothness of playback.
5. CDN Cache
   CDN (Content Delivery Network) is a distributed network service that can cache static resources by establishing servers around the world. When a user requests access to the resource, the CDN will automatically select the server closest to the user based on the user's IP address, thereby improving resource access speed. CDN caching makes full use of large-scale distributed server clusters to speed up the loading of web pages.

To sum up, the HTTP caching mechanism is a very important part of web development. It can significantly improve web page loading speed and user experience. Understanding common caching strategies and their principles is crucial to optimizing website performance and reducing server load. Developers should choose an appropriate caching strategy based on the actual situation, and reasonably set the cache expiration time and cache control rules, which can not only improve website performance but also ensure that users obtain the latest resources.

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