What Is Caching Data and How It Works?

What is caching data and how does cache work?

Caching Data or data caching is a process that stores multiple copies of data or files in a temporary storage location—or cache—so they can be accessed faster. It saves data for software applications, servers, and web browsers, which ensures users need not download information every time they access a website or application to speed up site loading.

Cached data typically includes multimedia such as images, files, and scripts, which are automatically stored on a device the first time a user opens an application or visits a website. This is used to quickly load the application or website’s information every time the user subsequently opens or visits it. Caching is a good solution for the von Neumann bottleneck, which looks at ways to better serve faster memory access.

A Domain Name System (DNS) caches DNS records to perform faster lookups, content delivery networks (CDNs) use caching to reduce latency, and web browsers cache requested Hyper Text Markup Language (HTML) files, images, and JavaScript to load websites faster. For example, when a user visits a website for the first time, an application or browser retains information to help them access it faster and more efficiently.

Cached data works by storing data for re-access in a device’s memory. The data is stored high up in a computer’s memory just below the central processing unit (CPU). It is stored in a few layers, with the primary cache level built into a device’s microprocessor chip, then two more secondary levels that feed the primary level. This data is stored until it's time to live (TTL), which indicates how long content needs to be cached for, expires or the device’s disk or hard drive cache fills up.

Data is typically cached in two ways, through browser or memory caching or through CDNs.

When a user visits a new website, their browser needs to download data to load and display the content on the page. To speed up this process for a user's future visit, browsers cache the content on the page and save a copy of it on the device hard drive. As a result, the next time the user goes to that website, the content is already stored on their device and the page will load faster.

Cache memory offers extremely low latency, which means it can be accessed quickly. As a result, it speeds up loading the second time a user accesses an application or website. However, a cache cannot store a lot of memory, so it only stores small files like images and web text.

Data can be cached in many ways, but it is typically reliant on the website’s owner to set a "header," which tells a device that data can be cached and for how long. This instructs a user’s browser what information to download and where to store the temporary files. The user can then create policies and preferences around what data they cache and even clear their whole cache to reduce the amount of data stored on their device.

Caching data is important because it helps speed up application performance and increase efficiency. It stores data locally, which means browsers and websites will load faster because access elements such as homepage images have previously been downloaded.

Internet users will typically leave a website that loads too slowly, which makes caching vital for website owners to improve user experience and encourage people to use their site. It is also important for online tools like Google Docs, which enable users to access and save their documents online.

However, there are downsides to caching data. Caching can improve browser performance, but it also risks users’ confidential or sensitive information being exposed to cyber criminals. Caching data could result in authentication data, browsing history, or session tokens being vulnerable, especially if a browser is left open or if another user has access to it.