Robots.Txt Explained
Web site owners use the /robots.txt file to give instructions about
their site to web robots; this is called The Robots Exclusion
Protocol.
It works likes this: a robot wants to vists a Web site URL, say
http://www.example.com/welcome.html. Before it does so, it firsts
checks for http://www.example.com/robots.txt, and finds:
User-agent: *
Disallow: /
The "User-agent: *" means this section applies to all robots.
The "Disallow: /" tells the robot that it should not visit any
pages on the site.
There are two important considerations when using /robots.txt:
-
robots can ignore your /robots.txt. Especially malware robots that scan the
web for security vulnerabilities, and email address harvesters used by spammers
will pay no attention.
-
the /robots.txt file is a publicly available file. Anyone can see what sections
of your server you don't want robots to use.
So don't try to use /robots.txt to hide information.
More details
Plese use some of the numerous external resources:
The rest of this page gives an overview of how to use /robots.txt on
your server, with some simple recipes.
How to create a /robots.txt file
Where to put it
The short answer: in the top-level directory of your web server.
The longer answer:
When a robot looks for the "/robots.txt" file for URL, it strips the
path component from the URL (everything from the first single slash),
and puts "/robots.txt" in its place.
For example, for "http://www.example.com/shop/index.html, it will
remove the "/shop/index.html", and replace it with
"/robots.txt", and will end up with
"http://www.example.com/robots.txt".
So, as a web site owner you need to put it in the right place on your
web server for that resulting URL to work. Usually that is the same
place where you put your web site's main "index.html" welcome
page. Where exactly that is, and how to put the file there, depends on
your web server software.
Remember to use all lower case for the filename:
"robots.txt", not "Robots.TXT.
What to put in it
The "/robots.txt" file is a text file, with one or more records.
Usually contains a single record looking like this:
User-agent: *
Disallow: /cgi-bin/
Disallow: /tmp/
Disallow: /~joe/
In this example, three directories are excluded.
Note that you need a separate "Disallow" line for every URL prefix you
want to exclude -- you cannot say "Disallow: /cgi-bin/ /tmp/" on a
single line. Also, you may not have blank lines in a record, as they
are used to delimit multiple records.
Note also that globbing and regular expression are
not supported in either the User-agent or Disallow
lines. The '*' in the User-agent field is a special value meaning "any
robot". Specifically, you cannot have lines like "User-agent: *bot*",
"Disallow: /tmp/*" or "Disallow: *.gif".
What you want to exclude depends on your server.
Everything not explicitly disallowed is considered fair
game to retrieve. Here follow some examples:
To exclude all robots from the entire server
User-agent: *
Disallow: /
To allow all robots complete access
User-agent: *
Disallow:
(or just create an empty "/robots.txt" file, or don't use one at all)
To exclude all robots from part of the server
User-agent: *
Disallow: /cgi-bin/
Disallow: /tmp/
Disallow: /junk/
To exclude a single robot
User-agent: BadBot
Disallow: /
To allow a single robot
User-agent: Google
Disallow:
User-agent: *
Disallow: /
To exclude all files except one
This is currently a bit awkward, as there is no "Allow" field. The
easy way is to put all files to be disallowed into a separate
directory, say "stuff", and leave the one file in the level above
this directory:
User-agent: *
Disallow: /~joe/stuff/
Alternatively you can explicitly disallow all disallowed pages:
User-agent: *
Disallow: /~joe/junk.html
Disallow: /~joe/foo.html
Disallow: /~joe/bar.html
Content of this tage were taken from robotstxt.org
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