Generating barcode for ISBN for print book cover design?

Eugene covered the QR vs EAN-13 difference well. One thing worth adding from the prepress side, since a barcode can scan fine on your phone and still be a problem at the printer:

1. Vector, not a picture. Place a PDF or EPS with real vector bars, not a PNG or JPG. Raster bars get soft edges at print resolution.
2. 100% K only. The bars should be C0 M0 Y0 K100. Some generators export rich black or RGB black, which prints on all four plates and blurs the gaps between bars if the plates shift. Check it in Acrobat: Print Production > Output Preview > Separations. The barcode must be on the Black plate only.
3. Place it at 100%. Do not scale it down to fit. KDP's barcode area is 2 x 1.2 in, and IngramSpark's cover template already has a barcode area.
4. White behind the bars, with the quiet zones on both sides kept clear.
5. Scan a printed proof, not only the screen, and compare the number with your ISBN.

Disclosure: I am a book cover designer and I built a free tool for this, Barcode Rocket (barcoderocket.com). It makes the ISBN barcode with the price add-on as a vector PDF in 100% Black, sized for KDP and IngramSpark, no account needed. Whatever tool you use, the checklist above is what keeps the cover from being sent back.

I just created a simple script  which does a pretty good job - it generates the barcode (EAN/ISBN-13) directly into the page – vectorial, fonts already converted to outlines, grouped and scaled to about 25 mm wide (that can be easily adjusted). If you are interested, check my GitHub repo. Of course, it’s completely free – and feel free to do anything you like with it - use it, distribuie it, modify it or whatever.
profun77/isbn13-barcode-indesign-script: Generate vector ISBN‑13 (EAN‑13) barcodes directly inside Adobe InDesign.

Hello

QR codes aren't the same thing as ISBN barcodes. The Generate QR Code feature in InDesign creates a QR code (usually a square code you scan with a phone) and it can contain text, web links, contact details and so on.

An ISBN barcode is different. It's the standard retail barcode you see on the back of books, made of vertical bars. ISBNs are encoded using the EAN-13 barcode format (typically), sometimes with an extra 5-digit price code on the side (EAN-5) if needed.

So typing an ISBN into the QR Code generator won't produce the correct barcode for book printing.

If you want to make an ISBN barcode, you can:

Use a free online generator, for example:
https://barcode.tec-it.com/en/ISBN13

Or use a dedicated tool or plugin if you want more control inside InDesign - for example:
https://www.barcodeproducer.com/articles/creating-real-barcodes-for-adobe-indesign

To test the barcode, just use any barcode scanner app on your phone or a handheld scanner if you have one. It should read the number exactly as your ISBN.