Website speed/Page speed is an important search engine ranking factor. Internet users prefer using fast loading web applications. If they come across a slow loading website, they'll exit the browser or close the tab that's opening the page. As bounce rate/exit rate of such websites is very high, they'll rank lower in search engine result pages than fast loading pages.
Page speed depends upon various factors. If the webpage size is large, the browser will take some time to open up the page.
The best way to reduce the size of the web-pages is enabling Gzip compression on the server. Gzip supports up to up to 9 compression levels. The highest level will result in the smallest size files but it may affect the performance of the web server. The lowest compression level is 1. It doesn't have any effect on the web-server. To enable GZip, you'll have to modify the server configuration file.
Once you modify the file you can test whether the Gzip compression is working on the web server or not or whether you've implemented Gzip compression correctly or not with the free Crawl Center Gzip checker tool.
To use the tool, enter the page URL in the textbox and click the Submit button.