Google Adsense recommends your site include an "ads.txt" file.
This file helps advertisers verify that your site is approved to use Google Adsense ads.
Using Google Adsense without this file will significantly reduce your earnings potential from Google Adsense.
Before you create this file, create a Google Adsense account thru Google. Once that is done, make a copy of your Google Adsense Publisher Id. Go to your account information page in Google Adsense to copy your Publisher Id:
Once your have your Publisher Id, create your ads.txt file.
To create this file, use a TEXT EDITOR on your computer and create a file named ads.txt. Note the name of this file must be in all lowercase.
The content of the file should look like the following:
google.com, YOURIDHERE, DIRECT, f08c47fec0942fa0
Replace "YOURIDHERE" with your Publisher Id.
Save the ads.txt file.
Using FTP, copy the ads.txt file you have created to the root directory of your website.
If you are using Filezilla, your Filezilla display will look similar to the following example:
Your site now has a properly formatted ads.txt file suitable for use with Google Adsense.