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Web metrics: Size and number of resources

Author: Sreeram Ramachandran, Software Engineer
Last updated: 26 May 2010

Here are some statistics about the size, number of resources and other such metrics of pages on the world wide web. These are collected from a sample of several billions of pages that are processed as part of Google's crawl and indexing pipeline. In processing these pages, we not only take into account the main HTML of the page, but also discover and process all embedded resources such as images, scripts and stylesheets.

Highlights:

• The average web page takes up 320 KB on the wire.
• Only two-thirds of the compressible material on a page is actually compressed.
• In 80% of pages, 10 or more resources are loaded from a single host.
• The most popular sites could eliminate more than 8 HTTP requests per page if they combined all scripts on the same host into one and all stylesheets on the same host into one.

Caveats:

• All resources are fetched using Googlebot, which means they are subject to robots.txt restrictions. For example, some sites (such as the BBC) block CSS and JS.
• Some sites may present a different view of the resources to Googlebot than to regular users. For example, until recently, Google's own servers used to serve CSS and JS uncompressed to Googlebot, while compressing them for regular user browsers.
• Pages are rendered and subresources are discovered through the eye of WebKit. If a page serves resources differently for Internet Explorer or Firefox, those won't be visible here.
• Sampling of pages for processing is not uniformly random or unbiased. For example, pages with higher PageRank are more likely to be included in these metrics.

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