What is cache and why?
Cache is a common concept in many areas of computing.
To put it as simply as possible: your cache is a local store of data that has been fetched from somewhere else (most often the internet), so that this data can be displayed more quickly if its needed in the same form again.
Cache within your browser
Before we talk about Joomla, let’s focus for a moment on browser cache.
The cache within your web browser aims to speed up the process of browsing the internet by storing a partial – or complete – copy of websites you’ve visited locally on your computer.
If you visit the same website again, your browser will sometimes choose to show the cached content rather than load the same content again from the internet. Since this data is stored locally, it can be displayed far more quickly than when loaded from the web.
Clearing the browser cache
Cache is a good thing to have, except when it isn’t.
Let’s say you’re making changes on your website. You change the relevant files, but when you refresh the site in your browser to see the changes, you still see the “old” version … because it’s been cached within your browser.
To see the changes you’ll need to delete the local version of your site from the browser cache, which will then cause the browser to automatically download the new one version on the next refresh.
Thankfully, clearing your browser cache is really easy:
- Chrome: Press CTRL + Shift + Del on your keyboard and click Clear data
- Edge: Press CTRL + Shift + Del on your keyboard and click Clear
- Internet Explorer: Press CTRL + Shift + Del on your keyboard and click Delete
- Firefox: Press CTRL + Shift + Del on your keyboard and click Clear Now
- Safari: Press Option + ⌘ + E on your keyboard
- Opera: Press CTRL + Shift + Del on your keyboard and click Clear data
What is Joomla cache?
The cache within Joomla is similar, but it’s also different.
Depending on the settings within your site, Joomla stores the requested in the /cache directory in your Joomla site root.
If the user requests a page that they’ve (or anyone else has) already visited, and nothing has changed on that page in the meantime, the content for that page doesn’t need to be generated from the database again.
Serving a cached version of the page is quicker and easier. If cache is activated, this version will be served instead until it the cache expires. The expiration period can be set in the Global Configuration within Cache Settings.
There are actually three levels of Joomla caching:
- Conservative caching – caches output from component views and modules
- Progressive caching – like (1) but also caches all module content
- Page caching – caches entire website pages
There are a few more settings as regards cache within the global configuration, but this is more than enough to understand the basics.
How can I clear the Joomla cache?
Clearing the Joomla cache is easy:
- Log in to the administrator area of your Joomla site
- Go to System -> Clear Cache
- Click the Delete All button (don’t worry, your data won’t be deleted, just temporary cache files)
Turning the cache off completely
If you’re making frequent changes on your Joomla site and would prefer to turn the cache off completely, this is also easy to change:
- Log in to the administrator area of your Joomla site
- Go to System -> Global Configuration
- Click the System tab
- Find Cache Settings and set System Cache to OFF – Caching disabled
Now you’ve disabled the Joomla cache and shouldn’t have problems with it. The only thing to remember: you might still need to clear your browser cache if you still have issues.
Joomla extensions for caching
Joomla has a native caching system and it works well, however if you want to extend the caching functionality there are a few Joomla extensions that promise to enhance your caching experience!
A few mentions:
- Speed Cache by JoomUnited
- JotCache by V.Kanich
- Page Cache Extended by Viktor Vogel
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