The back of your business card is blank. It is the most valuable space you own.

Business cards are printed two-sided and used one-sided. The back is blank, or it has your logo on it again, which is the same as blank.

It is also the only piece of advertising you hand to somebody who has just decided they are interested in you. That is a better position than any poster will ever be in, and most people spend it on a logo.

There are two things worth putting there. They are not the same thing, and which one you pick depends on why you are handing the card over.

Option one: a contact card code

A contact card code puts your name, number, email and company straight into their phone in one tap.

The value is not the seconds saved. It is that the details arrive spelled correctly, in the right fields, filed under your actual name — rather than being typed out of a photo of your card three weeks later, which is a thing that does not happen. A card in a drawer is a card that has failed. A contact in a phone is a contact.

Use this one when you want to be reachable. A trade, a supplier, a consultant, anybody whose next conversation is a phone call or an invoice.

Option two: a LinkedIn code

A LinkedIn code asks for a connection instead.

That does nothing for you today and quite a lot next quarter. A saved contact sits silently in a phone forever. A connection puts you in a feed, in front of somebody who will change jobs, need a supplier, or be asked for a recommendation at some point in the next two years.

Use this one at conferences, in consulting and recruitment, and anywhere the relationship matters more than the transaction.

Label it, or it will not get scanned

This is where most business card codes actually fail, and it is not technical.

A bare code on a card is a question. Is it a website? A vCard? A marketing thing that will sign me up to something? People do not scan questions while somebody is standing in front of them, and they do not remember to try later.

Three words fixes it. “Save my details”, or “Connect on LinkedIn”. The generator will print a caption under the code for you, sized and coloured to match, so it looks intentional rather than like something added in Word.

Name the outcome, not the mechanism. “Scan me” tells somebody what to do and not what they get, which is the wrong half.

Printing it on something that small

A business card is the smallest surface most people will ever print a code on, so two rules matter more here than anywhere else.

Print it at the size the file comes out at, and do not let a layout program scale it down to fit a corner. The size you are given is already the minimum that reads reliably — shrinking it by eight percent to make the layout tidy is how a card gets printed with a code that only works in good light.

And keep the pale border around it. That quiet margin is how a scanner finds the code at all, and trimming it to reclaim a few millimetres on a crowded card is the most common way a good code gets ruined at the printer. Give it clear space on all four sides and keep it away from the trim edge, because guillotines wander by a millimetre or two.

What not to put there

Your homepage. If somebody has your card they can type your domain, and a code that saves them eleven characters has spent the most valuable space on your card doing nothing.

A code that points at a page you might move. The card is printed; the address has to outlive it.

And nothing at all is still better than an unlabelled code nobody scans, so if you are not going to caption it, keep the logo.