Robots.txt is a simple text file that instructs web crawlers on how to crawl a website and is an important aspect of Search Engine Optimization (SEO). A site owner uses `robots.txt` to effectively guide search engines regarding pages not to be indexed. By doing this, a site owner brings Search Engine Optimization activities under control and prevents the crawling, and indexing of duplicate content and sensitive content.

History of `robots.txt`

The Robots Exclusion Protocol, or robots.txt, was invented in 1994 with the idea of providing standard ways for webmasters & crawlers to communicate with one another. Eventually, the standard was taken into account by major search engines such as Google, Bing, and Yahoo!.

How `robots.txt` Works

The `robots.txt` file must be placed in the root directory of a website. For example, it should be accessible at `https://www.example.com/robots.txt`.

It only takes a few steps to see how `robots.txt` works. Let's take a look:

Step 1: Crawlers Request Access

Start: When a web crawler (such as Googlebot) visits a website, it requests access to the `robots.txt` file first.
URL Request: The crawler requests access to the file, i.e., by accessing `https://www.example.com/robots.txt`.

Step 2: Server Response

File Retrieved: If the file exists, the web server responds with the content of the `robots.txt` file.
404 Error Handling: If the file does not exist, then the web server will return a 404 error, and the crawler has access to all content by default.

Step 3: Parsing the Directives

Read File: The crawler will read the directives in the `robots.txt` file. The crawler sees which user-agents (crawlers) the rules apply to and which directories or pages are disallowed or allowed.

Step 4: Following the Rules

The crawler decides based on the directives:

If the path is Disallowed - the crawler will not index or access this path.
If the path is Allowed - the crawler can index the content of that directory or page.

Step 5: Indexing Content

Allowed Crawling: The crawler will crawl the allowed pages and once again collect the data needed to present in the search results.
Disallowed Crawling: The crawler ignores disallowed directories/pages, so it does not index them.

Step 6: Maintenance

File Updates: The webmaster may update the `robots.txt` file whenever she/he/they chooses to specify parameters for crawler access.
Crawlers Revisit: Crawlers will periodically check the `robots.txt` file to determine whether the directives have changed.

How to locate the `robots.txt` File

Finding the `robots.txt` file for any website is very easy. Just follow these simple steps:

1. Open Your Web Browser: Launch any web browser such as Chrome, Firefox, or Safari.

2. Type the Website URL: In the address bar, type in the full URL of the website you want to check. For example, `https://www.example.com`.

3. Add `/robots.txt`: Once you've entered the website URL, add `/robots.txt`at the end of the URL. So now we'd enter `https://www.example.com/robots.txt`.

4. Press Enter: Once you've entered the URL, just press Enter and be taken to that specified URL.

5. View the File: If the website has a `robots.txt` file, it will appear. It will be in plain text. You can now see the directives that the website has put down in the file.

How to write & Submit the `robots.txt` File

A `robots.txt` file only needs a few steps to create and submit the file. Here is what you need to do:

Step 1: Create the `robots.txt` file

1. Open a Plain Text Editor: There are many plain text editors you can use, including Notepad (Windows), TextEdit (as a plain text file) (Mac), or you could use a code editor like VS Code.

2. Write your directives. Start by writing your `robots.txt` file in the proper syntax. Here are a few examples:

User-agent: *

Disallow: /private/
Allow: /public/

Sitemap: https://www.example.com/sitemap.xml

3. Save the File: Save the file as `robots.txt`. Make sure to save it using plain text format (not in Word or any other format).

Step 2: Upload the `robots.txt` File

1. Find Your Website's Root Directory: Use an FTP client (for example FileZilla) or your web hosting's control panel (for example cPanel) to access the files for your website.

2. Go to the Root Directory: This is usually the folder where your website files are located, with the folder title being `public_html` or similar.

3. Upload the File: Drag and drop the `robots.txt` file into the root directory. Make sure it's at the top level and not in one of the subfolders.

Step 3: Verify the `robots.txt` File

1. Open Your Web Browser: You will need to open any web browser.

2. Enter the URL: Write your website url and add `/robots.txt` to the end (for example: `https://www.example.com/robots.txt`)

3. Check That It Displays Correctly: Make sure that the file displays and follows the directives that you wrote.

Step 4: Validate the `robots.txt` File

1. Google Search Console:

- Log in to your Google Search Console account.

- Pick the website property you want to work with.

- Go to "Settings" > "Crawling" > "robots.txt".

- After this, click on open report to test your `robots.txt` file.

2. Bing Webmaster Tools:

- Log in to Bing Webmaster Tools

- Select Your Website Property

- Click on “Tools & Enhancements”>“robots.txt Tester”

- Validate Your robots.txt File

Step 5: Monitor and Update

- Regular Check: Perform an occasional check of your `robots.txt` file to make sure it reflects your current needs.

- Update as Needed: If you change your website structure or content, make changes in the `robots.txt` file as needed and re-upload it.

Example Structure:

User-agent: *

Disallow: /private/

User-agent: the crawler being specified.

Disallow: Indicates which paths should not be accessed.

Common Directives in `robots.txt`

Directive	Description	Example
User-agent	Identifies the web crawler	User-agent: Googlebot
Disallow	Block access to specified paths	Disallow: /private/
Allow	Permits access to specific paths	Allow: /public/
Crawl-delay	Sets a delay between requests	Crawl-delay: 10
Sitemap	Links to the sitemap for better indexing	Sitemap: https://www.example.com/sitemap.xml

Robots.txt Best Practices:

Keep it Simple: Your rules should be clear and unambiguous. Do not use complicated conditions.
Ensure Accessibility for Important Content: Be careful to allow access to the pages that are important to you.
Test the File: You can use tools such as Google Search Console to check for errors.
Update Regularly: Review the file regularly as your site changes over time.

Common Mistakes to Avoid

Error	Definition
Blocking Important Pages	Accidentally disallowing pages that should be indexed.
Misusing Disallow	Incorrectly blocking entire directories instead of specific files.
Failing to Test	Not using tools to verify the effectiveness of the file.
Ignoring User-Agent Specificity	Not considering different crawlers needs.

Testing Ensuring robots.txt is functional

- Google Search Console (use for robots.txt validation)

- web server logs (check bots that visited the blocked address)

- Robots.txt checkers (have some online options).

Example

Case Studies:

Amazon.com

- Use robots.txt to block specific paths to optimize crawling, e.g.

    User-agent: *

    Disallow: /gp/cart

2. YouTube:

- Disallows user-specific pages to protect privacy.

- Example:

     user-agent: *

     Disallow: /login

youtube robots.tx file

Advanced Topics

Dynamic Generation: Some sites may generate `robots.txt` based on user sessions or as content is updated.
As Part of your SEO Strategy: Use the `robots.txt` file in conjunction with the use of meta tags as well as canonical links to optimize for SEO.
Performance considerations: A well-designed `robots.txt` can potentially increase your site speed by reducing the load on the server for disallowed files.

Conclusion

In summary, `robots.txt' is a valuable resource for webmasters to achieve some control of how web crawlers behave. Webmasters who check and frequently update the `robots.txt' file will help enhance the SEO of their websites. As a webmaster, such a basic understanding of the structure and directive values in 'robots.txt' files is essential.

Robots.txt Guide: How It Works, Best Practices & SEO Impact