Prioritize visible content

PageSpeed Service was turned off on August 3rd, 2015. Please see Turndown Information for PageSpeed Service.

Objective

To speed up web pages by prioritizing visible content of the page.

Description

This is a new rewriter, so please preview your site as described here, to ensure that it works for your site before making it live.

This rewriter renders the visible content much sooner by:

  1. Prioritizing visible content: Rendering a modern web page requires lots of network resources but not all of them are needed right away. Visible content of the page is prioritized on the network and the browser so it doesn’t have to compete with the rest of the page.
  2. Defer JavaScript: JavaScript is deferred until page load so that it doesn’t block rendering of page content.

Example

The effect of this rewriter on this page can be observed before and after rewriting.

Operation

  1. When a user visits your site, the browser requests the page from PSS.
  2. PSS requests the page from your origin site.
  3. PSS processes the response, extracts the visible portions from the full HTML and sends it to the browser.
  4. PSS injects JavaScript that has the browser bind the below-the-fold portions into the page.

Limitations

  1. This rewriter works on modern browsers - IE9, Firefox 3+, Chrome, Safari. It is not applied on pages served for mobile devices, tablets and all other user agents.

Troubleshooting

  • Defer JavaScript is a pre-requisite for this rewriter so if your site breaks with Defer JavaScript, you cannot use this rewriter.