Website page size is important when it comes to SEO. If the size of the page is large, it will take some time to load on the website visitor's browser. Many times, people simply abandon such pages causing a high bounce/exit rate. If the page size is low, it will open quickly in the browser.
Confused? Well, let's consider an example of an ISO file of the Windows or Linux OS and a document you've uploaded to your Google Drive. The size of the ISO files can be 1+ GB and a document can be of a few kilobytes size. As the size of the document is low, it will be downloaded to your PC within a few seconds or minutes (if the file is few megabytes large). The browser may take 30 to several hours to download the ISO file. To make sure that people don't exit the page without going through it, you should keep its size on the lower side.
With this tool, you can see the size of the web page. To use this tool, simply enter the page URL in the textbox and click the "Check size" button. When you do so, the tool will display the size of the page in bytes and kilobytes. Once you optimize the page, you can re-check it for free. You can test the page as many times as you want.