Robots txt file tips

Introduction Robots.txt file

Robots.txt is a text (not html) file you put on your site to tell search robots which pages you would like them not to visit. Robots.txt is by no means mandatory for search engines but generally search engines obey what they are asked not to do. It is important to clarify that robots.txt is not a way from preventing search engines from crawling your site (i.e. it is not a firewall, or a kind of password protection) and the fact that you put a robots.txt file is something like putting a note “Please, do not enter” on an unlocked door – e.g. you cannot prevent thieves from coming in but the good guys will not open to door and enter. That is why we say that if you have really sensitive data, it is too naive to rely on robots.txt to protect it from being indexed and displayed in search results.

The location of robots.txt in a website is very important. It must be in the root directory because otherwise user agents (search engines) will not be able to find it – they do not search the whole site for a file named robots.txt. Instead, they look first in the main directory (i.e. http://mysite.com/robots.txt) and if they don't find it there, they simply assume that this site does not have a robots.txt file and therefore they index everything they find along the way. So, if you don't put robots.txt in the proper place, do not be surprised that search engines index your whole site. 

 Create Your Robots.txt file

So lets get moving. Create a regular text file called "robots.txt", and make sure it's named exactly that. This file must be uploaded to the root accessible directory of your site, not a sub directory (ie: http://www.mysite.com but NOT http://www.mysite.com/stuff/). It is only by following the above two rules will search engines interpret the instructions contained in the file. Deviate from this, and "robots.txt" becomes nothing more than a regular text file, like Cinderella after midnight.

Now that you know what to name your text file and where to upload it, you need to learn what to actually put in it to send commands off to search engines that follow this protocol (formally the "Robots Exclusion Protocol"). The format is simple enough for most intents and purposes: a USERAGENT line to identify the crawler in question followed by one or more DISALLOW: lines to disallow it from crawling certain parts of your site.

1) Here's a basic "robots.txt": 

User-agent: *
Disallow: /

With the above declared, all robots (indicated by "*") are instructed to not index any of your pages (indicated by "/"). Most likely not what you want, but you get the idea.

2) Lets get a little more discriminatory now. While every webmaster loves Google, you may not want Google's Image bot crawling your site's images and making them searchable online, if just to save bandwidth. The below declaration will do the trick:

User-agent: Googlebot-Image
Disallow: /

3) The following disallows all search engines and robots from crawling select directories and pages:

User-agent: *
Disallow: /cgi-bin/
Disallow: /privatedir/
Disallow: /tutorials/blank.htm

4) You can conditionally target multiple robots in "robots.txt." Take a look at the below:

User-agent: *
Disallow: /
User-agent: Googlebot
Disallow: /cgi-bin/
Disallow: /privatedir/

This is interesting- here we declare that crawlers in general should not crawl any parts of our site, EXCEPT for Google, which is allowed to crawl the entire site apart from /cgi-bin/ and /privatedir/. So the rules of specificity apply, not inheritance.

5) There is a way to use Disallow: to essentially turn it into "Allow all", and that is by not entering a value after the semicolon(:): 

User-agent: *
Disallow: /
User-agent: ia_archiver
Disallow:

Here I'm saying all crawlers should be prohibited from crawling our site, except for Alexa, which is allowed.

6) Finally, some crawlers now support an additional field called "Allow:", most notably, Google. As its name implies, "Allow:" lets you explicitly dictate what files/folders can be crawled. However, this field is currently not part of the "robots.txt" protocol, so my recommendation is to use it only if absolutely needed, as it might confuse some less intelligent crawlers.
Per Google's FAQs for webmasters, the below is the preferred way to disallow all crawlers from your site EXCEPT Google:

User-agent: *
Disallow: /
User-agent: Googlebot
Allow: /