Working With The robots.txt File
- What is the robots.txt file?
- Working with the robots.txt file
- Advantages of robots.txt
- Disadvantages of the robots.txt file
- Optimization of the robots.txt file
- Using the robots.txt file
What is the robots.txt file
The robots.txt file is an ASCII text file that has specific instructions for search engine robots about specific content that they are not allowed to index. These instructions are the deciding factor of how a search engine indexes your website's pages. The universal address of the robots.txt file is: www.example.com/robots.txt. This is the first file that a robot visits. It picks up instructions for indexing the site content and follows them. This file contains two text fields. Lets study this robots.txt example :
The User-agent field is for specifying robot name for which the access policy follows in the
Disallow field specifies URLs which the specified
robots have no access to. An example :
* means all robots and
/ means all URLs. This is read as, "No access
for any search engine to any URL" Since all URLs are preceded by
/ so it
bans access to all URLs when nothing follows after
/. If partial access has
to be given, only the banned URL is specified in the
Disallow field. Lets consider
this example :
# Research access for Googlebot.
Here we see that both the fields have been repeated. Multiple commands can
be given for different user agents in different lines. The above commands mean
that all user agents are banned access to /concepts/new/ except Googlebot which
has full access. Characters following
# are ignored up to the line termination
as they are considered to be comments.
Working with the robots.txt file
- The robots.txt file is always named in all lowercase
- Wildcards are not supported in both the fields. Only
*can be used in the
User-agentfields' command syntax because it is a special character denoting "all". Googlebot is the only robot that now supports some wildcard file extensions. Ref: http://www.google.com/webmasters/faq.html#12
- The robots.txt file is an exclusion file meant for search engine robot reference and not obligatory for a website to function. An empty or absent file simply means that all robots are welcome to index any part of the website.
- Only one file can be maintained per domain.
- Website owners who do not have administrative rights cannot sometimes make a robots.txt file. In such situations, the Robots Meta Tag (http://www.seorank.com/meta-tags-article.htm) can be configured which will solve the same purpose. Here we must keep in mind that lately, questions have been raised about robot behavior regarding the Robot Meta Tag. Some robots might skip it altogether. Protocol makes it obligatory for all robots to start with the robots.txt thereby making it the default starting point for all robots.
- Separate lines are required for specifying access to different user agents
Disallowfield should not carry more than one command in a line in the robots.txt file. There is no limit to the number of lines though i.e. both the
Disallowfields can be repeated with different commands any number of times. Blank lines will also not work within a single record set of both the commands.
- Use lower-case for all robots.txt file content. Please also note that filenames on Unix systems are case sensitive. Be careful about case sensitivity when defining directory or files for Unix hosted domains.
You can use The robots.txt Validator to check your robots.txt from www.searchengineworld.com.
Advantages of the robots.txt file
Protocol demands that all search engine robots start with the robots.txt file.
This is the default entry point for robots if the file is present. Specific
instructions can be placed on this file to help index your site on the web.
Major search engines will never violate the Standard for Robots Exclusion.
- The file can be used to keep out unwanted robots like email retrievers, image strippers etc.
- It can be used to specify the directories on your server that you don't want robots to access and/or index e.g. temporary, cgi, and private/back-end directories.
- An absent robots.txt file could generate a 404 error and redirect the robot to your default 404 error page. Here it was noticed after careful research that sites that do not have a robots.txt file present and had a customized 404-error page, would serve the same to the robots. The robot is bound to treat it as the robots.txt file, which can confuse it's indexing.
- The file is used to direct select robots to relevant pages to be indexed. This specially comes in handy where the site has multilingual content or where the robot is searching for only specific content.
- The need for the file was also felt to stop robots from deluging servers with rapid-fire requests or re-indexing the same files repeatedly. If you have duplicate content on your site for any reason, the same can be controlled from getting indexed. This will help you avoid any duplicate content penalties.
Disadvantages of the robots.txt file
Careless handling of directory and filenames can lead hackers to snoop around your site by studying the file, as you sometimes may also list filenames and directories that have classified content. This is not a serious issue as deploying some effective security checks to the content in question can take care of it. For example if you have your traffic log on your site on a URL such as www.example.com/stats/index.htm which you do not want robots to index, then you would have to add a command to your robots.txt file. As an example:
However, it is easy for a snooper to guess what you are trying to hide and simply typing the URL www.example.com/stats in his browser would enable access to the same. This calls for one of the following remedies:
- Change file names:
- Change the stats filename from index.htm to something different, such as stats-new.htm so that your stats URL now becomes www.example.com/stats/stats-new.htm
- Place a simple text file containing the text, "Sorry you are not authorized to view this page", and save it as index.htm in your/stats/directory.
- Use login passwords:
- Password-protect the sensitive content listed in your robots.txt file.
Optimization of the robots.txt file
The right commands:
Use correct commands. Most common errors include: putting
the command meant for
User-agent field in the
Disallow field and vice-versa.
Please also note that there is no "Allow" command in the standard robots.txt
protocol. Content not blocked in the
Disallow field is considered allowed.
Currently, only two fields are recognized: The
User-agent field and the
field. Experts are considering the addition of more robot recognizable commands
to make the file more Webmaster and robot friendly.
Note - Google is the only search engine, which is experimenting with
certain new robots.txt commands. There are indications that Google now
Please refer to: http://www.google.com/webmasters/faq.html#12
Do not put multiple file URLs in one Disallow line in the file. Use a new Disallow line for every directory that you want to block access to. Incorrect example :
Disallow: /concepts/ /links/ /images/
Files and directories:
If a specific file has to be disallowed, end it with the file extension and without a forward slash in the end. Study the following example :
Remember if you have to block access to all files in the directory, you don't have to specify each and every file in robots.txt. You can simply block the directory as shown above. Another common error is leaving out the slashes altogether. This would leave a very different message than intended.
The right location:
No robot will access a badly placed robots.txt file. Make sure that the location is www.example.com/robots.txt.
Never capitalize your syntax commands. Directory and filenames are case sensitive
in Unix platforms. The only capitals used per standard are:
If you want to block access to all but one or more than one robot, then the specific ones should be mentioned first. Lets study this example:
In the above case, MSNBot would simply leave the site without indexing after reading the first command. The correct syntax is:
Not having the file at all could generate a 404 error for search engine robots, which could redirect the robot to the default 404-error page or your customized 404-error page. If this happens seamlessly, it is up to the robot to decide if the target file is a robots.txt file or an HTML file. Typically it would not cause many problems but you may not want to risk it. It's always a better idea to put the standard robots.txt file in the root directory, than not having it at all.
The standard robots.txt file for allowing all robots to index all pages is:
Using # carefully in the file:
Adding comments after the syntax commands is not a good idea using
Some robots might misinterpret the line although it is acceptable as per the
exclusion standard. New lines are always preferred for comments.
Using the robots.txt file
- Robots are configured to read text. Too much graphic content could render your pages invisible to the search engine. Use the file to block irrelevant and graphic-only content.
- Indiscriminate access to all files, it is believed, can dilute relevance to your site content after being indexed by robots. This could seriously affect your site's ranking with search engines. Use the robots.txt file to direct robots to content relevant to your site's theme by blocking the irrelevant files or directories.
- The file can be used for multilingual websites to direct robots to relevant content for relevant topics for different languages. It ultimately helps the search engines to present relevant results for specific languages. It also helps the search engine in its advanced search options where language is a variable.
- Some robots could cause severe server loading problems by rapid firing too many requests at peak hours. This could affect your business. By excluding some robots that might be irrelevant to your site, in the robots.txt file, this problem can be taken care of. It is really not a good idea to let malevolent robots use up precious bandwidth to harvest your emails, images etc.
- Use the file to block out folders with sensitive information, text content, demo areas or content yet to be approved by your editors before it goes live.
The robots.txt file is an effective tool to address certain issues regarding website ranking. Used in conjunction with other SEO strategies, it can significantly enhance a website's presence on the net.
Article last updated : 11th March 2004
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(c) Copyright 2004 Jagdeep.S. Pannu, SEORank
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