Digital Marketing Handbook

Robots Exclusion Standard 164

Nonstandard extensions

Crawl-delay directive

Several major crawlers support a Crawl-delay parameter, set to the number of seconds to wait between

successive requests to the same server:[5][6][7]

User-agent: *

Crawl-delay: 10

Allow directive

Some major crawlers support an Allow directive which can counteract a following Disallow directive.[8] [9]

This is useful when one tells robots to avoid an entire directory but still wants some HTML documents in that

directory crawled and indexed. While by standard implementation the first matching robots.txt pattern always wins,

Google's implementation differs in that Allow patterns with equal or more characters in the directive path win over a

matching Disallow pattern.[10] Bing uses the Allow or Disallow directive which is the most specific.[11]

In order to be compatible to all robots, if one wants to allow single files inside an otherwise disallowed directory, it

is necessary to place the Allow directive(s) first, followed by the Disallow, for example:

Allow: /folder1/myfile.html

Disallow: /folder1/

This example will Disallow anything in /folder1/ except /folder1/myfile.html, since the latter will match first. In case

of Google, though, the order is not important.

Sitemap

Some crawlers support a Sitemap directive, allowing multiple Sitemaps in the same robots.txt in the form:[12]

Sitemap: http://www.gstatic.com/s2/sitemaps/profiles-sitemap.xml

Sitemap: http://www.google.com/hostednews/sitemap_index.xml

Universal "*" match

the Robot Exclusion Standard does not mention anything about the "*" character in the Disallow: statement.

Some crawlers like Googlebot and Slurp recognize strings containing "*", while MSNbot and Teoma interpret it in

different ways.[13]

References

[ 1 ]http:/ / http://www. robotstxt. org/ orig. html#status

[ 2 ]http:/ / http://www. robotstxt. org/ norobots-rfc. txt

[ 3 ]http:/ / http://www. youtube. com/ watch?v=KBdEwpRQRD0#t=196s

[ 4 ]http:/ / http://www. robotstxt. org/ wc/ norobots. html

[ 5 ]"How can I reduce the number of requests you make on my web site?" (http:/ / help. yahoo. com/ l/ us/ yahoo/ search/ webcrawler/ slurp-03.

html). Yahoo! Slurp.. Retrieved 2007-03-31.

[ 6 ]"MSNBot is crawling a site too frequently" (http:/ / search. msn. com/ docs/ siteowner.

aspx?t=SEARCH_WEBMASTER_FAQ_MSNBotIndexing. htm& FORM=WFDD#D). Troubleshoot issues with MSNBot and site crawling..

Retrieved 2007-02-08.

[ 7 ]"About Ask.com: Webmasters" (http:/ / about. ask. com/ en/ docs/ about/ webmasters. shtml#15)..

[ 8 ]"Webmaster Help Center - How do I block Googlebot?" (http:/ / http://www. google. com/ support/ webmasters/ bin/ answer. py?hl=en&

answer=156449& from=40364).. Retrieved 2007-11-20.

[ 9 ]"How do I prevent my site or certain subdirectories from being crawled? - Yahoo Search Help" (http:/ / help. yahoo. com/ l/ us/ yahoo/

search/ webcrawler/ slurp-02. html).. Retrieved 2007-11-20.