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What is cached data? Your device’s secret stash

Web cache works invisibly in your browser to speed up web surfing. Here’s what you need to know about what it is and how it works.

There are many factors that may impact speed and responsiveness when browsing the internet.

Some of those factors are external, such as the available bandwidth and speed of your internet plan, to name just a couple.

However, some speed-impacting factors can be internal to your device.

One of these potential factors is called ‘web cache’ (also called ‘HTTP cache’ or just ‘cache’), and it’s designed to work invisibly to help speed up web browsing.

The purpose of cache

Generally speaking, web cache is designed as an invisible convenience, designed to reduce loading times when revisiting webpages.

When you visit a website for the first time on a device, the browser you’re using downloads all the relevant resources that are required to ‘load’ the webpage, such as text, images, etc.

Web cache helps to speed up subsequent visits by avoiding the need to re-download some of those resources the next time you load that same page, or load a new page on the same website that uses identical elements (think of a persistent logo image).

Temporarily storing certain info helps to speed up loading times by reducing the perceived lag, decreasing the load on the web server (which hosts the website/s we visit), and reducing bandwidth usage.

This is how web cache reduces the loading times of previously visited webpage, compared to the first visit to a webpage, which had not been cached before.

Where is it stored?

The web cache itself is stored on the device that’s being used to browse the website, and cached data is stored on a per-browser basis.

This means, for example, if you were to visit the nbn™ website using the Google Chrome browser on a laptop, then visit the nbn™ website again using the Microsoft Edge browser on the same device, your laptop would download and store the relevant cached data for both browsers.

After your first visit in Google Chrome or Microsoft Edge on the same device, though, the next time you use either of those browsers to visit the nbn™ website, that browser will use its cache to avoid re-downloading certain resources.

Viewing your cached data

Most browsers will let you view your cached data.

For instance, if you use Google Chrome, you can type ‘chrome://cache’ into the URL bar to see a list of website items that have been cached on the device you’re currently using to surf the web.

The method for viewing cached data changes between browsers. If you’re interested, try a web search to find the method on your specific browser.

Used-by data

Ideally, the local presence of web cached data eliminates the need to re-download the same website data every time you revisit it.

However, certain conditions have to be met for a browser to prioritise your cached resources over those stored on the website, even when revisiting. After all, your cached data might be out of date.

Web cache is measured and compared to the online resources it’s reflecting in terms of some key factors, including 'freshness' and 'validation'.

'Freshness' and 'validation' refer to a process that ensures your cached data is up to date with and reflective of what’s stored and displayed on the cached website.

If the cached data is out of date, it will be re-downloaded and updated in the locally stored web cache on a per-browser basis.

Downsides of web cache

Web cache is collected automatically and usually by default when you use a web browser.

This takes up storage space on the local device.

However, browsers tend to limit the amount of data they store as part of downloaded web cache, which means each browser will automatically delete old data to keep the web cache at a manageable size.

Anyone who has access to the same connected device and its web browsers also has access to your browsing history via cache (if they know where to look).

Web cache can be erased on your browsers by using the ‘erase private browsing data’ (or similarly worded) function.

Remember, cache is only viewable for people who have direct access to your device, such as a shared computer.

Cookies vs cache

Web cache and web cookies both operate invisibly in the background within browsers as we surf the web, but they serve different functions.

Web cookies are primarily used to store information that relates to user information, and may be used to offer personalised browsing or advertising.

Web cache is used to store resource files client-side on a device, unless manually removed by a user, to speed up the browsing process.

You can read more about web cookies here.

Web cache is useful for automatically speeding up the responsiveness of the websites we regularly visit on particular devices with particular browsers, but it’s worth looking into manually clearing web cache at regular intervals or browsing in private modes if you have privacy concerns or your device is very short on storage space.

Good online habits are important. Don't forget to check out our article on password safety, to make sure you're not making any simple security mistakes.

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