I was using the online generator (http://www.terryburton.co.uk/
barcodewriter/generator/) and I noticed that ISBN 13 output includes
an extra ">" character at the end.

This is true for the default sample included and for an ISBN entry I
entered with or without a price.

I have never seen an ISBN barcode with the ">" at the end.

Can this be used?

Is this a bug?

Thanks,

The feature that you refer to is known as a whitespace guard and it is
not directly read by a barcode scanner. Its purpose is to discourage
people from designing into the whitespace border immediately to the
left and right or the bars which would make scanning more error-prone.

Its use is entirely optional, but is especially encouraged if you
thing that you are unlikely to quality check the barcode prior to
final publication.

If you want to get rid of it the simple remove the "guardwhitespace" option.

All the best,