How to Fix Invalid Robot.txt File Formats

A well-functioning website cannot operate without the robots.txt file. This helps the search engine crawlers discover which parts of a given web resource should be searched first and which can be ignored. 

Two types of issues may arise from an invalid robots.txt configuration. The first problem is that it can prevent search engines from indexing publicly accessible sites, which would reduce the visibility of your content in organic search results. 

Secondly, it can encourage search engines to crawl and index pages that you would rather not have visible in organic search results. This article will help you to deal with invalid robot.txt file format issues.

How do I Resolve Issues with the Robot.txt File?

  • Avoid 5XX HTTP Status Codes

The most important thing to verify on your robots.txt file is that it never sends back an HTTP 5XX status code, as this means you’re having an issue with your server. With this mistake, search engines won’t know which sites you want them to crawl and therefore, they won’t bother trying to index any fresh content.

  • Your robots.txt File Should be 500 KB or Less

The robots.txt file shouldn’t be bigger than 500 kilobytes (KB) to prevent search engines from giving up halfway through processing.

But what if you have a large site with a lot of pages?

Instead of blocking individual pages, try blocking categories of similar pages. For example, if you want to block PDF files from being crawled, block all URLs that end in .pdf rather than including them individually with:

disallow: /*.pdf

  • Pay Attention to Formatting Errors

Note that only the “name: value” format for comments, directives, and blank lines is allowed in the robots.txt file. Here are two rules to follow:

  1. Both allow and disallow values must be empty or start with / or *.
  2. When you’re writing a value, avoid putting a $ sign in the midst of it.
  • User-Agent Requires a Value 

To properly direct a search engine’s crawlers, you must assign a value to each user-agent. To specify a particular search engine crawler, you must select a user-agent name from the public list.

Using * will ensure a proper match for any and all mismatched crawlers.

Undefined User Agent:


disallow: /downloads/

General User Agent and a “magicsearchbot” User Agent are Defined:

user-agent: *

disallow: /downloads/

user-agent: magicsearchbot

disallow: /uploads/

  • Do Not Put Allow or Disallow Directives Before the User-Agent

If you don’t include an instruction after the initial user-agent name in the robots.txt file, the search engine crawlers won’t know what to do with the rest of the file.

Additionally, crawlers will give more weight to a more particular user-agent name, so if given a choice between user-agent: * and user-agent: Googlebot-Image, the latter will be followed.

Common issues include:

No Search Engine Spiders Read the Disallow: /downloads Directive:

# start of file

dissallow: /downloads/

user-agent: magicsearchbot

allow: /

All Web Spiders Are Dissallowed to Index the /downloads Folder:

# start of file

user-agent: *

disallow: /downloads/

  • Sitemaps Must Be Specified with an Absolute URL

It is essential to give search engines a sitemap file so they can better understand the pages on your website. In most cases, this will include an up-to-date list of all the URLs on your website and information regarding the most recent updates.

Make sure you use an absolute URL if you want to include a sitemap file in the robots.txt file.


sitemap: /sitemap-file.xml



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