What is a cache?
A cache is a temporary storage layer that holds frequently used data so that it can be accessed faster. On a website, a cache keeps elements of a page such as HTML files, CSS stylesheets, JavaScript files and media files, so that they do not have to be loaded from the server again on every single page view.
The benefit of caching lies in shorter loading times and in a lower load on the server, because the files are stored closer to the visitor and can therefore be delivered more quickly.
Which types of cache are there for websites?
- Browser cache: the web browser stores data of a website on the device of the visitor. When that visitor opens the page again, the browser loads the stored data, which shortens the loading time.
- Server cache: this type of cache sits on the web server. Frequently requested content is held there so the server can answer requests faster. That lowers the server load and improves response times.
- Content delivery network (CDN) cache: a CDN distributes copies of website content across servers in different geographic locations. Visitors then receive the content from the server closest to them, which cuts the loading time considerably.
- Application cache: some web applications use a cache of their own to store data and states temporarily, which is particularly helpful for dynamic applications.
How does caching affect SEO?
Caching plays a substantial role in search engine optimization. A faster loading time gives visitors a better experience, and that is an important factor for search engines like Google, which put a number on it with the Core Web Vitals. Pages that load quickly tend to rank higher in the search results. Effective caching also lowers the bounce rate, because visitors are less likely to leave a page that is there right away.
An efficient cache also lets the web crawlers of search engines work through the content of a website faster and more effectively, which spends the available crawl budget on more pages and improves visibility and indexing. Caching therefore matters not only for the user experience, but also for how visible a website is in search engines.
Whether your caching is set up correctly, and where it still costs you loading time, is one of the points we look at in an SEO audit.
