Your Robots.txt file is what tells the search engines which pages to access and index on your website on which pages not to. For example, if you specify in your Robots.txt file that you don’t want the search engines to be able to access your thank you page, that page won’t be able to show up in the search results and web users won’t be able to find it. Keeping the search engines from accessing certain pages on your site is essential for both the privacy of your site and for your SEO.
This article will explain why this is and provide you with the knowledge of how to set up a good Robots.txt file.
How Robots.txt Work
Search engines send out tiny programs called “spiders” or “robots” to search your site and bring information back to the search engines so that the pages of your site can be indexed in the search results and found by web users. Your Robots.txt file instructs these programs not to search pages on your site which you designate using a “disallow” command. For example, the following Robots.txt commands:
Source: Seo Site Checkup