Did you know that after buying your ISBN, you don't actually have to pay for the barcode? Many agencies like Bowker offer a barcode for an extra fee (often around $25), but as a self-published author, you can get this for free.
Tools like Kindlepreneur or Bookow allow you to enter your ISBN-13 and generate a print-ready file in seconds.
An ISBN is the unique 13-digit identifier for your book; the barcode is just the scannable image of that number.
If you publish through platforms like Amazon KDP or IngramSpark , they can often generate and place the barcode on your cover automatically.