Hello @greenhouse2 and thanks for your question. This post here lists Square compatible barcode scanners. Some are wired and some are bluetooth wireless. It will depend on what hardware you're using and what you're comfortable using. I have a traditional wired barcode scanner attached to my Square Register, running the basic POS software. I make and print my own barcodes from a page layout program and print on my laser printer on a sheet of small labels.

As far as the format for barcodes, there are some standard formats like UPC-A, EAN-8, etc... but really any apha-numberic sequence can make a barcode. You'll need to check with the barcode scanner manufacturer you select and see what formats they can read.

There are also other factors about barcodes to successfully print and scan for Square. I've used free online websites that generate several formats of barcodes from whatever "barcode" I create. Many of my items are handmade so they don't have a manufacturer's barcode preprinted, so I tend to use smaller length SKU numbers I make up, like "ABC1...ABC2...etc." It doesn't matter what you choose as long as the barcode scanner can read it. I also use either Code 29 or Code 128 which create smaller barcodes (I like this format because my price labels are smaller).Here is some more info on different barcode formats.

You also have to test how large or small you need to print your barcodes to have a scanner read it. Sometimes I've printed large barcodes on my inkjet printer and the barcode doesn't come out clear enough to read it). Note, there are also fonts that can create barcodes but you usually need a page layout software and experience installing and using different fonts for this method.

Whatever method you decide on, it may take some trial and error but you'll develop a system of creating and printing barcodes that will successfully work with your chosen barcode scanner.