What are the browser caching mechanisms?

Browser caching mechanisms include strong cache, negotiation cache, Service Worker and IndexedDB, etc. Detailed introduction: 1. Strong caching. When the browser requests a resource, it will first check whether there is a copy of the resource in the local cache and whether the copy has expired. If the copy of the resource has not expired, the browser will directly use the local cache and will not Send a request to the server, thereby speeding up the loading of web pages; 2. Negotiate cache. When the copy of the resource expires or the browser's cache is cleared, the browser will send a request to the server, etc.

# Operating system for this tutorial: Windows 10 system, Dell G3 computer.

Browser caching mechanism refers to a series of caching strategies and mechanisms adopted by browsers to improve user experience and speed up web page loading when accessing web pages. The browser caching mechanism can help users reduce network requests, save bandwidth, and increase the loading speed of web pages when they visit the same web page again. The following will introduce several common methods of browser caching mechanisms.

Strong cache

Strong cache means that when the browser requests a resource, it will first check whether a copy of the resource exists in the local cache and whether the copy has expired. If the copy of the resource has not expired, the browser uses the local cache directly without sending a request to the server, thus speeding up the loading of web pages. The implementation of strong caching relies on two fields in the HTTP response header: Expires and Cache-Control. Expires is a specific expiration time, and the browser will determine whether the resource has expired based on this time; Cache-Control is a relative time that can specify the validity time of the resource.

Negotiate cache

When the copy of the resource expires or the browser's cache is cleared, the browser will send a request to the server to ask whether the resource has been updated. The server will determine whether the resource has been updated based on the last modification time of the resource or ETag (entity tag). If the resource is not updated, the server will return a 304 Not Modified response, telling the browser to use the local cache directly. The implementation of negotiated caching relies on the If-Modified-Since and If-None-Match fields in the HTTP request header, and the Last-Modified and ETag fields in the HTTP response header.

Service Worker

Service Worker is a script that runs in the background of the browser and can intercept network requests and process them. Through Service Worker, developers can customize caching strategies to achieve a more flexible and efficient caching mechanism. For example, developers can cache the static resources required for a web page locally and obtain them directly from the local cache the next time they visit without having to send a request to the server. This method can greatly improve the loading speed of web pages, especially when the network environment is poor or the network is disconnected, it can still provide basic page access functions.

IndexedDB

IndexedDB is a client database provided by the browser, which can store a large amount of structured data and supports transaction operations. Developers can use IndexedDB to store the data required for web pages locally to improve the loading speed and performance of web pages. When the user visits the web page again, the browser can obtain the data directly from IndexedDB without having to send a request to the server. This method can greatly reduce network overhead and improve user access experience.

Summary:

The browser caching mechanism is a series of strategies and strategies to improve web page loading speed and performance through strong caching, negotiated caching, Service Worker and IndexedDB. mechanism. By rationally utilizing the caching mechanism, developers can effectively reduce network overhead and improve user access experience. At the same time, the browser caching mechanism also requires developers to set reasonable caching strategies to ensure that users can obtain the latest data and resources in a timely manner. In actual development, developers need to have an in-depth understanding of the browser caching mechanism in order to choose the appropriate caching method according to specific needs and scenarios, thereby improving web page performance and user experience.

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