Have you ever been on a website and noticed a formatting issue that was just too weird to pawn-off on bad design? Or maybe something on a page that was there previously is gone/moved since the last time you visited? Well these could very well be because of your browser's cache. Having problems like this at work may lead to calling the IT staff and the first thing they will tell you to do is to try clearing your browser cache. So, what is the deal with the cache and why does refreshing it often solve browser problems?
First off, what is a cache?
The word cache (pronounced like kash) refers to something that is stored somewhere. And in computing, it is no different. A browser's cache is kind of like a form of memory. When visiting a website, your browser requests all the files needed to display it on your screen and stores them. It makes that request to a server that hosts the site, but if you already have those files downloaded (in your cache) then the page loads quicker as you do not need to download everything, just the changes/updates. This is called a 'read cache' as the browser can read the data on the cache to display the images on the site. This reduces bandwidth usage on both parties (client and server) and is especially useful when you have slow or limited connection to the internet. Web browsers like Chrome, Internet Explorer, Edge, Firefox, or Opera all use a cache to aide in visiting site you have previously accessed. It would be crazy to have to download the google logo every single time you go to google.com. Subsequently, this is why when your internet is down, the google homepage (in this example) seems to work fine until you try to search for something. Those images, JS (java script) scripts and CSS styles (cascading style sheet, what web pages use for layout and design) have already been downloaded from a past experience. This is similar to how cookies work where you do not have to enter information that your browser already knows. Read more about browser cookies here.
So why would I need to clear it?
The browser cache can build up over a long period of time. This, consequently, can take up a lot of space on your hard drive. Some of the data is from sites that you may never visit again, so clearing just grants more room for data from sites you visit often. While you can put a cap on the limit of the cache size, it is still very useful to clear it occasionally. For instance, say a site you go to a lot has a website overhaul and is completely updated. They may still be using the same file hierarchy on their side and have just changed styles and images. This can be quite confusing to your browser and may force it to display a mix of the new and old. This gives you a bad user experience and you might not even be able to find what you were looking for on that site.
In addition to possibly breaking formatting on a website, the cache can be a privacy issue. The cache captures data from every site visited and depending on who has access to your machine, they may see what sites and other web information has been gathered even after clearing browser's history. It can also help developers working on a site. They can use the browser console and simply disable the cache. This allows them to work on a website and make changes without having to clear the cache at all.
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Here is a great resource on how to clear your cache on most modern browsers.