Introduction:

Caching is the process of storing copies of files in a cache, or temporary storage location, so that they can be accessed more quickly. Technically, a cache is any temporary storage location for copies of files or data, but the term is often used in reference to Internet technologies. Web browsers cache HTML files, JavaScript, and images in order to load websites more quickly, while DNS servers cache DNS records for faster lookups and CDN servers cache content to reduce latency. To understand how caches work, consider real-world caches of food and other supplies. When explorer Roald Amundsen made his return journey from his trip to the South Pole in 1912, he and his men subsisted on the caches of food they had stored along the way. This was much more efficient than waiting for supplies to be delivered from their base camp as they traveled. Caches on the Internet serve a similar purpose; they temporarily store the 'supplies', or content, needed for users to make their journey across the web.

What does it do?

Every time a user loads a webpage, their browser has to download quite a lot of data in order to display that webpage. To shorten page load times, browsers cache most of the content that appears on the webpage, saving a copy of the webpage's content on the device’s hard drive. This way, the next time the user loads the page, most of the content is already stored locally and the page will load much more quickly. Browsers store these files until their time to live (TTL) expires or until the hard drive cache is full. (TTL is an indication of how long content should be cached.) Users can also clear their browser cache if desired.

CDN CACHING:

A CDN, or content delivery network, caches content (such as images, videos, or webpages) in proxy servers that are located closer to end users than origin servers. (A proxy server is a server that receives requests from clients and passes them along to other servers.) Because the servers are closer to the user making the request, a CDN is able to deliver content more quickly.

Other kinds of Caching:

DNS caching takes place on DNS servers. The servers store recent DNS lookups in their cache so that they do not have to query nameservers and can instantly reply with the IP address of a domain. Search engines may cache webpages that frequently appear in search results in order to answer user queries even if the website they are attempting to access is temporarily down or unable to respond.