When a webpage loads on your screen there are a lot of little pieces that have come together to create what you’re seeing. Your logo, other images, style sheets, javascript files are among some of the external resources a webpage might use to render itself on your screen. Generally, each time you load the page, every one of those resources has to be requested again, and served up to render the page.
Enter Leveraging Your Browser Caching.
A cache is a set of stored resources for your webpage/website. It holds those elements (external resources) in the browser so that the next time the page needs to be rendered a separate request does not need to be initiated, the browser already has those elements handy to render up the page for you. This makes pages much faster and increases the quality of the user experience … particularly on mobile. There are a number of different ways to leverage browser caching. Most common is through use of an .htaccess file. This file tells browsers what elements and resources to cache, and for how long. It may look something like the following.
## EXPIRES CACHING ##
<IfModule mod_expires.c>
ExpiresActive On
ExpiresByType image/jpg “access 1 year”
ExpiresByType image/jpeg “access 1 year”
ExpiresByType image/gif “access 1 year”
ExpiresByType image/png “access 1 year”
ExpiresByType text/css “access 1 month”
ExpiresByType text/html “access 1 month”
ExpiresByType application/pdf “access 1 month”
ExpiresByType text/x-javascript “access 1 month”
ExpiresByType application/x-shockwave-flash “access 1 month”
ExpiresByType image/x-icon “access 1 year”
ExpiresDefault “access 1 month”
</IfModule>
## EXPIRES CACHING ##
This would tell the browser to hold on to some elements (images) for a year and other files for a period of 1 month. It is important to note that when caching your external resources you will want to clear that cache when you make any changes to the website. If you don’t, the changes might not be served up when the page is called until the cache expires. For instance, changing a jpeg image on the site with a new one won’t redner for anyone that has a browser recognizing that jpegs are cached for 1 year. After that year, they’ll see the image change.