Make the Web Faster

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.
MetricTop SitesAll SitesDescription
Pages380 million4.2 billionNumber of sample pages analyzed.
Resources42.1443.91Average number of resources per page.
GETs42.6344.56Average number of GETs per page. Similar to number of resources, but also includes redirects.
Hosts8.397.01Average number of unique hostnames encountered per page.
Resources Per Host5.026.26Average number of resources per host (derived from the 'Resources' and 'Hosts' values).
Network Size/KB312.04320.24Average size transferred over the network per page, including HTTP headers. If resources were compressed, this would use the compressed size.
Document Size/KB477.26376.67Average uncompressed size of a page and its resources, excluding HTTP headers.
Zippable Size/KB287.51170.16Average uncompressed size of the compressible resources on a page, i.e., those with a Content-Type of 'text/*' or equivalent.
Unzipped Size/KB32.6757.07Average size of the compressible resources that were not sent compressed, i.e., the Content-Type was 'text/*', but Content-Encoding did not include 'gzip' or 'deflate'.
Zipped Ratio89%66%Average percentage of compressible bytes that were actually compressed (derived from the 'Zippable' and 'Unzipped' values).
Images27.5829.39Average number of unique images per page.
Image Size/KB184.73205.99Average network size of the images per page.
Scripts6.757.09Average number of external scripts per page.
Script Size/KB66.4857.98Average network size of the external scripts per page.
Combinable Scripts4.753.75Average number of requests that could be saved per page if external scripts on the same host were combined.
Stylesheets4.073.22Average number of external stylesheets per page.
Stylesheet Size/KB27.1718.72Average network size of the external stylesheets per page.
Combinable Stylesheets3.542.02Average number of requests that could be saved per page if external stylesheets on the same host were combined.
SSL Pages650 thousand17 millionNumber of sample SSL (HTTPS) pages analyzed.
SSL Hosts6.393.23Average number of unique hostnames encountered per SSL page.
SSL Zippable/KB263.58160.47Average size of the compressible resources per SSL page.
SSL Unzipped/KB133.7489.36Average size of the compressible resources that were not sent compressed, per SSL page.
SSL Zipped Ratio49%44%Average percentage of compressible bytes that were actually compressed, per SSL page (derived from the 'SSL Zippable' and 'SSL Unzipped' values).
MetricTierMeanMin10203040Median60708090Max
GETs Per PageTop Sites42.631172125283339486081977
All Sites44.5611018243037455466862,758
Hosts Per PageTop Sites8.391334478101217222
All Sites7.01112345781014374
KB Per PageTop Sites312.040.0038.1580.44119.28145.51176.23208.38275.48377.16597.08312,426.25
All Sites320.240.0021.8254.1590.76131.30177.47234.67310.51428.73663.19517,026.13
KB Per HostTop Sites37.180.000.731.763.926.7311.1817.1226.7555.45132.76311,872.59
All Sites45.690.000.781.943.606.9613.0923.9744.1285.15179.08441,631.71
KB Per GETTop Sites7.320.000.460.681.061.602.363.194.767.7616.7514,852.58
All Sites7.190.000.430.630.921.311.932.904.387.9618.4635,932.92
GETs Per HostTop Sites5.081.002.112.883.504.505.626.758.009.2011.25401.00
All Sites6.361.002.333.294.205.146.257.609.3312.0818.001,045.00
Max GETs Per HostTop Sites-15912151821263339860
All Sites-1610151924293644592,754

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