So you heard about someone stressing the importance of the robots.txt file, or noticed in your website’s logs that the robots.txt file is causing an error, or somehow it is on the very top of the top visited pages, or, you read some article about the death of the robots.txt file and about how you should not bother with it ever again. Or maybe you never heard of the robots.txt file but are intrigued by all that talk about spiders, robots and crawlers. In this article, I will hopefully make some sense out of all of the above.
There are many folks out there who vehemently insist on the uselessness of the robots.txt file, proclaiming it obsolete, a thing of the past, plain dead. I disagree. The robots.txt file is probably not in the top ten methods to promote your get-rich-fast affiliate website in 24 hours or less, but still plays a major role in the long run.
First of all, roboticsengineeringandgameplay the robots.txt file is still a very important factor in promoting and maintaining a site, and I will show you why. Second, the robots.txt file is one of the simple means by which you can protect your privacy and/or intellectual property. I will show you how.
Let’s try to figure out some of the lingo.
What is this robots.txt file?
The robots.txt file is just a very plain text file (or an ASCII file, as some like to say), with a very simple set of instructions that we give to a web robot, so the robot knows which pages we need scanned (or crawled, or spidered, or indexed – all terms refer to the same thing in this context) and which pages we would like to keep out of search engines.
What is a www robot?
A robot is a computer program that automatically reads web pages and goes through every link that it finds. The purpose of robots is to gather information. Some of the most famous robots mentioned in this article work for the search engines, indexing all the information available on the web.
The first robot was developed by MIT and launched in 1993. It was named the World Wide Web Wander and its initial purpose was of a purely scientific nature, its mission was to measure the growth of the web. The index generated from the experiment’s results proved to be an awesome tool and effectively became the first search engine. Most of the stuff we consider today to be indispensable online tools was born as a side effect of some scientific experiment.
What is a search engine?
Generically, a search engine is a program that searches through a database. In the popular sense, as referred to the web, a search engine is considered to be a system that has a user search form, which can search through a repository of web pages gathered by a robot.
What are spiders and crawlers?
Spiders and crawlers are robots, only the names sound cooler in the press and within metro-geek circles.
What are the most popular robots? Is there a list?
Some of the most well known robots are Google’s Googlebot, MSN’s MSNBot, Ask Jeeves’s Teoma, Yahoo!’s Slurp (funny). One of the most popular places to search for active robot info is the list maintained at http://www.robots.org.
Why do I need this robots.txt file anyway?
A great reason to use a robots.txt file is actually the fact that many search engines, including Google, post suggestions for the public to make use of this tool. Why is it such a big deal that Google teaches people about the robots.txt? Well, because nowadays, search engines are not a playground for scientists and geeks anymore, but large corporate enterprises. Google is one of the most secretive search engines out there. Very little is known to the public about how it operates, how it indexes, how it searches, how it creates its rankings, etc. In fact, if you do a careful search in specialized forums, or wherever else these issues are discussed, nobody really agrees on whether Google puts more emphasis on this or that element to create its rankings. And when people don’t agree on things as precise as a ranking algorithm, it means two things: that Google constantly changes its methods, and that it does not make it very clear or very public. There’s only one thing that I believe to be crystal clear. If they recommend that you use a robots.txt (“Make use of the robots.txt file on your web server” – Google Technical Guidelines), then do it. It might not help your ranking, but it will definitely not hurt you.
There are other reasons to use the robots.txt file. If you use your error logs to tweak and keep your site free of errors, you will notice that most errors refer to someone or something not finding the robots.txt file. All you have to do is create a basic blank page (use Notepad in Windows, or the most simple text editor in Linux or on a Mac), name it robots.txt and upload it to the root of your server (that’s where your home page is).
On a different note, nowadays, all search engines look for the robots.txt file as soon as their robots arrive on your site. There are unconfirmed rumors that some robots might even ‘get annoyed’ and leave, if they don’t find it. Not sure how true that is, but hey, why not be on the safe side?
Again, even if you don’t intend to block anything or just don’t want to bother with this stuff at all, having a blank robots.txt is still a good idea, as it can actually act as an invitation into your site.
Don’t I want my site indexed? Why stop robots?
Some robots are well designed, professionally operated, cause no harm and provide valuable service to mankind (don’t we all like to “google”). Some robots are written by amateurs (remember, a robot is just a program). Poorly written robots can cause network overload, security problems, etc. The bottom line here is that robots are devised and operated by humans and are prone to the human error factor. Consequently, robots are not inherently bad, nor inherently brilliant, and need careful attention. This is another case where the robots.txt file comes in handy – robot control.
Now, I’m sure your main goal in life, as a webmaster or site owner is to get on the first page of Google. Then, why in the world would you want to block robots?
Here are some scenarios:
1. Unfinished site
You are still building your site, or portions of it, and don’t want unfinished pages to appear in search engines. It is said that some search engines even penalize sites with pages that have been “under construction” for a long time.
Always block your cgi-bin directory from robots. In most cases, cgi-bin contains applications, configuration files for those application (that might actually have sensitive information), etc. Even if you don’t currently use any CGI scripts or programs, block it anyway, better safe than sorry.
You might have some directories on your website where you keep stuff that you don’t want the entire Galaxy to see, such as pictures of a friend who forgot to put clothes on, etc.
4. Doorway pages
Besides illicit attempts to increase rankings by blasting doorways all over the internet, doorway pages actually do have a very morally sound usage. They are similar pages, but each one is optimized for a specific search engine. In this case, you must make sure that individual robots do not have access to all of them. This is extremely important, in order to avoid being penalized for spamming a search engine with a series of extremely similar pages.
5. Bad bot, bad bot, what’cha gonna do…
You might want to exclude robots whose known purpose is to collect email addresses, or other robots whose activity does not agree with your beliefs on the world.
6. Your site gets overwhelmed
In rare situations, a robot goes through your site too fast, eating your bandwidth or slowing down your server. This is called “rapid-fire” and you’ll notice it if you are reading your access log file. A medium performance server should not slow down. You may however have problems if you have a low performance site, such as one running of your personal PC or Mac, if you run poor server software, or if you have heavy scripts or huge documents. Is these cases, you’ll see dropped connections, heavy slowdowns, in extremes, even a complete system crash. If this ever happens to you, read your logs, try to get the robot’s IP or name, read the list of active robots and try to identify and block it.
What’s in a robots.txt file anyway?
There are only two lines for each entry in a robots.txt file, the User-Agent, which has the name of the robot you want to give orders or the ‘*’ wildcard symbol meaning ‘all’, and the Disallow line, which tells a robot all the places it should not touch. The two line entry can be repeated for every file or directory you don’t want indexed, or for each robot you want to exclude. If you leave the Disallow line empty, this means you are not disallowing anything, in other words, you are allowing the particular robot to index your entire site. Some examples and a few scenarios should make it clear:
A. Exclude a file from Google’s main robot (Googlebot):
B. Exclude a section of the site from all robots:
Note that the directory is enclosed between two forward slashes. Although you are probably used to see URLs, links and folder references that do not end with a slash, note that a web server always needs a slash at the end. Even when you see links on websites that do not end with a slash, when that link is clicked, the web server has to do and extra step before serving the page, which is adding the slash through what we call a redirect. Always use the ending slash.
C. Allow everything (blank robots.txt):
Note that when a “blank robots.txt” is mentioned, it is not a completely blank file, but it contains the two lines above.
D. Do not allow any robot on your site:
Note that the single forward slash means “root”, which is the main entrance to your site.
E. Do not allow Google to index any of your images (Google uses Googlebot-Image for images):
F. Do not allow Google to index some of your images:
Note the use of multiple disallows. This is allowed, no pun intended.
G. Build a doorway for Google and Lycos (the Lycos robot is called T-Rex) – do not play with this unless you are 100% sure you know what you are doing:
H. Allow only Googlebot..
Note that the commands are sequential. The example above reads in English: Let Googlebot through, then stop everyone else.
If your file gets really large, or you just feel like writing notes for yourself or for potential viewers (remember, robots.txt is a public file, anyone can see it), you can do so by preceding your comment with a # sign. Although according to the standard, you can have a comment on the same line with a command, I recommend that you start every command and every comment on a new line, this way, robots will never be confused by a potential formatting glitch. Examples:
This is correct, as per the standard, but not recommended (a newer robot or a badly written one might read the following as “disallow the # We… Directory”, not complying to the “disallow all” command):
User-Agent: * Disallow: / # We decided to stop all robots but we were very silly in typing a long comment which got truncated and made the robots.txt unusable
The way I recommend that you format this is:
# We decided to stop all robots and we made sure
# that our comments do not get truncated
# in the process
Although theoretically, each robot should comply to the standards introduced around 1994 and enhanced in 1996, each robot acts a little differently. You are advised to check the documentation provided by the owners of those robots, you’ll be surprised to discover a world of useful facts and techniques. For instance, from Google’s site we learn that Googlebot completely disregards any URL that contains “&id=”.
Here are some sites to check:
A database of robots is maintained at [http://www.robotstxt.org/wc/active/html/contact.html]
A robots.txt validation tool – invaluable in finding potential typos that can completely change the way search engines see your site, can be found at: [http://searchengineworld.com/cgi-bin/robotcheck.cgi]
There are also some extensions to the standard. For example, some robots allow wildcards in the Disallow line, some even allow different commands. My advice is: don’t bother with anything outside the standard and you will not be unpleasantly surprised.
A final word of caution:
In this article I showed you how things should work in a perfect world. Somewhere along this article I mentioned that there are good bots and bad bots. Let’s stop for a moment and think from a deranged person’s perspective. Is there anything to prevent one from writing a robot program that reads a robots.txt file and specifically look at pages that you marked as “disallowed”? The answer is absolutely not, this entire standard is based on the honor system and is based on the concept that everyone should work hard to make the internet a better place. Basically, do not rely on this for real security or privacy. Use passwords when necessary.
In conclusion, do not forget that indexing robots are your best friends. While you shouldn’t build your site for robots, but for your human visitors, do not underestimate the power of those mindless crawlers – make sure the pages you want to be indexed are clearly seen by robots, make sure you have regular hyperlinks that robots can follow without roadblocks (robots can’t follow Flash based navigation systems, for instance). To keep your site at tip top performance, to keep your logs clean, your applications, scripts and private data safe, always use a robots.txt file and make sure you read your logs to monitor all robotic activity.
Andrei co-owns Bsleek – a company that specializes in web design, hosting, promotional items, printing, tradeshow displays, logos, CD presentations, SEO and more [http://www.bsleek.com/]. Andrei has amassed an extensive technical knowledge and experience through his career as the CIO for a major travel management company and through his past careers in military research, data acquisition and airspace engineering. He also consults for Trinity Investigations