2D barcode
A 2D barcode is read in two directions at once, so it holds far more than the striped kind.
What the word means
An ordinary striped code is read across, and only across. The height of the bars carries nothing: it is there so that a scanner passed at an angle still crosses them all. Such a code holds about a dozen digits — a reference, and nothing else.
A 2D code uses the height as well. It is a grid, and every square of the grid carries something. That is a change of scale rather than a small gain: a few hundred to a few thousand characters instead of a dozen. A whole address, a payment, a delivery line.
What it does on a real document
On an invoice, a QR code at the foot of the page carries the account to pay, the exact amount and the reference. The person paying points a telephone at it and the transfer is filled in for them.
Such a code is drawn on the page like any other shape, in solid black rectangles. It stays sharp at any size, which a photograph of a code would not, and it comes out the same on paper as on screen.
Where it comes from, and why
Striped codes reached shops in the 1970s and did what was asked of them for years. What broke them was industry wanting the information itself on the object, rather than a number pointing into a database somewhere else.
Several answers appeared over the twenty years that followed, each shaped by the job it was made for: a tiny square for small parts, a wide flat one for identity documents, one made to be read off a lit screen. Each is a standard in its own right, and none of them replaced the others.
See it on a finished document
Glossary
- QR code
- The square of black and white dots you point a phone at: on a poster, on a restaurant table, at the foot of a bill. It carries a web address, or the exact details of a payment, so nobody has to type anything in. On an invoice it turns paying into one tap.