The Sitemaps protocol allows a webmaster to inform search engines about URLs on a website that are available for crawling. A Sitemap is an XML file that lists the URLs for a site. It allows webmasters to include additional information about each URL: when it was last updated, how often it changes, and how important it is in relation to other URLs in the site. This allows search engines to crawl the site more intelligently. Sitemaps are a URL inclusion protocol and complement robots.txt, a URL exclusion protocol.

Sitemaps are particularly beneficial on websites where:

• some areas of the website are not available through the browsable interface, or
• webmasters use rich Ajax, Silverlight, or Flash content that is not normally processed by search engines.

Sitemaps supplement and do not replace the existing crawl-based mechanisms that search engines already use to discover URLs. Using this protocol does not guarantee that web pages will be included in search indexes, nor does it influence the way that pages are ranked in search results.^{[citation needed]}

History[link]

Google first introduced Sitemaps 0.84 in June 2005 so web developers could publish lists of links from across their sites. Google, MSN and Yahoo announced joint support for the Sitemaps protocol in November 2006. The schema version was changed to "Sitemap 0.90", but no other changes were made.

In April 2007, Ask.com and IBM announced support for Sitemaps. Also, Google, Yahoo, MS announced auto-discovery for sitemaps through robots.txt. In May 2007, the state governments of Arizona, California, Utah and Virginia announced they would use Sitemaps on their web sites.

The Sitemaps protocol is based on ideas^[1] from "Crawler-friendly Web Servers".^[2]

File format[link]

The Sitemap Protocol format consists of XML tags. The file itself must be UTF-8 encoded. Sitemaps can also be just a plain text list of URLs. They can also be compressed in .gz format.

A sample Sitemap that contains just one URL and uses all optional tags is shown below.

<source lang=xml> <?xml version="1.0" encoding="utf-8"?>

<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">

   <url>
       <loc>http://example.com/</loc>
       <lastmod>2006-11-18</lastmod>
       <changefreq>daily</changefreq>
       <priority>0.8</priority>
   </url>

</urlset> </source>

Element definitions[link]

The definitions for the elements are shown below:^[3]

Support for the elements that are not required can vary from one search engine to another.^[3]

Sitemap index[link]

The Sitemap XML protocol is also extended to provide a way of listing multiple Sitemaps in a 'Sitemap index' file. The maximum Sitemap size of 10 MB or 50,000 URLs means this is necessary for large sites. As the Sitemap needs to be in the same directory as the URLs listed, Sitemap indexes are also useful for websites with multiple subdomains, allowing the Sitemaps of each subdomain to be indexed using the Sitemap index file and robots.txt.

Other formats[link]

Text file[link]

The Sitemaps protocol allows the Sitemap to be a simple list of URLs in a text file. The file specifications of XML Sitemaps apply to text Sitemaps as well; the file must be UTF-8 encoded, and cannot be more than 10 MB large or contain more than 50,000 URLs, but can be compressed as a gzip file.^[3]

Syndication feed[link]

A syndication feed is a permitted method of submitting URLs to crawlers; this is advised mainly for sites that already have syndication feeds. One stated drawback is this method might only provide crawlers with more recently created URLs, but other URLs can still be discovered during normal crawling.^[3]

Search engine submission[link]

If Sitemaps are submitted directly to a search engine (pinged), it will return status information and any processing errors. The details involved with submission will vary with the different search engines. The location of the sitemap can also be included in the robots.txt file by adding the following line to robots.txt:

Sitemap: <sitemap_location>

The <sitemap_location> should be the complete URL to the sitemap, such as: http://www.example.org/sitemap.xml (however, see the discussion). This directive is independent of the user-agent line, so it doesn't matter where it is placed in the file. If the website has several sitemaps, this URL can simply point to the main sitemap index file.

The following table lists the sitemap submission URLs for several major search engines:

Sitemap URLs submitted using the sitemap submission URLs need to be URL-encoded, replacing : with %3A, / with %2F, etc.^[3]

Sitemap limits[link]

Sitemap files have a limit of 50,000 URLs and 10 megabytes per sitemap. Sitemaps can be compressed using gzip, reducing bandwidth consumption. Multiple sitemap files are supported, with a Sitemap index file serving as an entry point. Sitemap index files may not list more than 50,000 Sitemaps and must be no larger than 10MiB (10,485,760 bytes) and can be compressed. You can have more than one Sitemap index file.^[3]

As with all XML files, any data values (including URLs) must use entity escape codes for the characters ampersand (&), single quote ('), double quote ("), less than (<), and greater than (>).

See also[link]

• Biositemap
• Metadata
• Resources of a Resource
• Yahoo! Site Explorer
• Google Webmaster Tools

References[link]

External links[link]

• Official page (set up by Google, Yahoo & MSN)
• Google, Yahoo, MSN joint announcement in Nov'06
• Official Blog
• Google Sitemaps newsgroup (archived)
• Google Sitemaps newsgroup
• Sitemap Gen Python script to generate Sitemaps by Google
• sitemap_gen.py Python script to generate Sitemaps by Google with MemoryError fixed
• Search::Sitemap Perl Library for manipulating Sitemaps
• PHP Sitemap Class A PHP Class for creating sitemaps
• XmlSitemapGenerator.org A free online tool for creating sitemaps