What is a cache?

A cache is any reserved data storage location that helps software or hardware run faster.

You’ve probably come across the term “cache” in the context of computing. Your browsers and apps use it, and so does the CPU (central processing unit) in your computer and mobile device. You may have even had to clear your cache on occasion.  

What does cache mean?

So, what is a cache, and why is it so critical in computing? A cache is any reserved data storage location that helps software or hardware run faster. Meanwhile, caching is the process of utilizing cache.  

Think of a cache as a small drawer under your office desk that holds temporary files you need to access frequently. Sure, you can store the files in a large file cabinet, but keeping them in the drawer speeds up your productivity. Of course, you may need to remove some of the files when they become obsolete or overload the drawer.

What is cached data in browsers, and why should you clear it?  

A browser's cache stores website data so that websites load faster the next time you visit them. Instead of downloading the same data again, your computer loads them quickly from your cache. Website cache is especially convenient for computers with slower Internet connections. Here are some examples of what browser cache stores:

  • HTML pages
  • CSS stylesheets
  • Images
  • Downloads
  • Site location data

While a browser cache may help websites load faster, it can slow down your computer, especially if the cache grows too big and resides on the same partition as your operating system (OS). Deleting cached files may also help fix formatting or loading issues on websites. For example, you may be seeing an outdated application form on a website if you don’t clear your cache.

Are cache and cookies the same thing?

Although they seem similar, cache and cookies aren't the same things. While a cache holds website resources like media files to enhance loading time, cookies are text files that save your website browsing preferences. Deleting both cookies and cache can enhance your data privacy in certain circumstances. You can check how to clear cookies if you want to minimize your digital footprint or want to delete your cookies on a public computer for security.  

What is DNS cache?

To help you understand DNS cache, we should probably address the obvious question: what does DNS mean? Short for Domain Name System, DNS is an Internet protocol that translates URLs to their numeric IP addresses. Computers need these IP addresses to identify websites.

Like other types of cache, DNS cache helps improve efficiency. It’s a temporary database on your computer that maintains a record of the domains you try to visit. When you enter a domain name in your browser, your computer can find the public IP address faster through the locally stored DNS cache instead of relying on an online DNS nameserver.

What is DNS cache poisoning?

While DNS cache is valuable, it's susceptible to DNS cache poisoning. Threat actors can poison DNS caches by spoofing DNS nameservers and redirecting traffic to themselves. To learn more about this type of attack, read our article: DNS hijacks: what to look for

What is cached data on my phone?

Just like any computer, your mobile devices use cache to load websites faster. But overgrown cache folders can be counterproductive as they may slow down a system or load an outdated version of a website. Fortunately, it’s easy to learn how to clear cache on an iPhone or any other mobile device. 

Apps and cache

Apps usually have their own cache like save files, data, images, and videos that they can reload quickly. For example, the communication app, WhatsApp, stores information about your messages in its cache, and it even holds sent media files for easy access. But when such cache files grow, they can take up precious space on a device with limited storage like a mobile phone.

CPU cache

You probably know that a computer uses its central processing unit (CPU) to interact with software, performing many calculations in a second. To enhance efficiency, a CPU utilizes a little slice of memory near the processor core called the CPU cache. The CPU cache is critical because it carries frequently used data and instructions from further memory locations like RAM (Random Access Memory). There are several grades of CPU cache:

  • L1 is typically part of the CPU chip and is usually the fastest and smallest CPU cache.
  • L2 and L3 are usually slower than L1 but are also larger. You can typically find L2 and L3 between the CPU and the RAM on the motherboard.


Your computer’s hardware and software both have a cache, and sometimes it is necessary to clear it. Clearing cache may require visiting your app’s settings, or simply restarting the computer, depending on the nature of the files.

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