What is a cache? Everything you need to know

Definition of cache

A cache is a store of data on your device that can be used to speed up loading times. They’re usually built into the infrastructure of an app.

Browsing the internet is essentially a never-ending exchange of information. Whether you’re using a browser or any other app on your phone or laptop, every click is a request for specific pieces of data, and everything you see on your screen is an answer to one of those requests.

But displaying a website with all its images and code can take a lot of time. To speed up that process, web browsers save some of that information and use it the next time you visit that same website. This is called caching. Cached data usually resides in the memory of an app on your device, but in some situations, you can also set up a cache server specifically for the purpose of caching. These servers are sometimes referred to as caching proxy servers.

Cached data systems aren’t limited to web browsers, of course. Every device and its apps use cache memory to speed up data access. But they don’t use cached data in the same way. For example, disk cache is used to load information preemptively for device functionality, while browsers and other apps save data from your previous activity, so certain sites and page elements can be loaded faster.

What is cached data?

Cached data is any information stored in a cache. Nearly every application, whether it’s your Chrome browser, a favorite social media app, or the device’s preinstalled fitness tracker, is storing — or caching — data.

This data could include almost anything from page text and image assets to the contents of private messages and drafted posts. Any material that can be loaded a little faster from the cache is stored, making load times just a little shorter.

To clarify, deleting cached data won’t have any impact on the data stored on a platform’s servers. If you clear your Instagram cache, for example, all your Instagram data is still accessible, it will just have to be loaded from the company’s servers, rather than from your app’s cache.

The benefits of cache memory

The main benefit of caching is speed. Because of their caches, browsers, apps, and operating systems are able to display information faster. But that’s not the only benefit.

Storing data locally means that you save bandwidth as you don’t have to download the same things again. And, because data is already on your device, you can sometimes use apps or view information in offline mode.

Downsides of cache systems

Despite its original purpose, caching can also reduce your device’s performance capabilities. This can happen in a number of ways:

• Caching uses old data. Cached data may prevent a website or app from using its newer version. It can stop images from loading and slow down the device in general. Caches use a dirty bit system to try to prevent this from happening, but it’s still a fairly common occurrence.
• Your cache collects data without your knowledge or consent. The only reason a cache exists is to collect data. But since caching is a background process, many people aren’t aware of how much old data is being stored on their device.
• Malware can hide in your cache. Despite being labeled as temporary memory, it can take months before your cache is deleted. That makes it a perfect place for hackers to hide their malware. This is not to be confused with cache poisoning, which involves hackers corrupting DNS caches.
• Cached data takes up storage space. Games, podcasts, videos, and social media apps store a lot of cached data on your device. That can add up to many gigabytes of precious storage.

Types of cache memory

Have you ever had a computer shut down on you suddenly? And when you turned it back on, did some of the apps relaunch so you could continue your work? That’s the benefit of caching. And it’s everywhere.

Memory cache

Memory cache uses CPU memory to speed up the data access from the main memory. It’s called L1, L2, L3, etc. and while it’s much smaller than RAM memory, it’s also much faster.

Disk cache

Disk cache uses RAM memory to create a copy of whatever you’re working on. Usually, the entire folder is copied into the cache because the computer assumes that you will be needing some of that data. That’s why the first time you open a folder might take significantly more time than opening a file inside it.

Browser cache (web cache)

Web browsers use your hard drive to store different parts of the web pages you visit like images, JavaScript, and queries. If you go to your browser settings and select to delete your history, you should also see how much storage has been used for cached images.

App cache

An app cache works just like a web cache. It saves bits of data like code and files to the app’s memory so it can retrieve them faster the next time you need them.

What does "clear cache" mean?

To clear cache just means deleting all the data currently saved inside your cache. This can be a good thing to do under a number of circumstances.

Clearing cache should be one of the first things you do if you are experiencing errors or if apps start to misbehave. But under normal circumstances, you should delete the cache at least once a month.

How to clear cache

Clearing cache involves a different process depending on your device and operating system. We have many guides that walk you through the steps on different platforms and apps:

• For a comprehensive guide, start with our article on how to clear cache, covering a wide range of devices and systems.
• Our article on how to clear cache on Google Chrome focuses on one of the most popular browsers.
• Firefox users should see our guide for how to clear cache on Mozilla Firefox.
• If you’re a console gamer, you might want to read our guide on how to clear cache on Xbox One.
• Outlook email app users should check the tutorial about how to clear cache on Microsoft Outlook.

Keep in mind that most guides on how to delete cookies and temporary files will also explain how to clear cache in the same process.