ISO vs ANSI layout: What’s the difference?

In my keyboard reviews I mentioned the ISO and ANSI layouts and said that I find ISO more comfortable when typing, but I didn’t discuss the topic that much in-depth. Chances are that you’ve already head of keyboard layouts when you were shopping for one. But the term layout can be used in two different meanings.

A little bit of history

The origins of keyboards as we know them today can be traced back to the early 1870s, after Remington had purchased the Sholes and Glidden typewriter with the intention to market it as the Remington No. 1. Back then there was no accepted standards for how letters should be placed on a typing machine keyboard. The Linotype, introduced in 1884, used a ETAOIN layout based on the distribution of letters in English words, whereas other manufacturers used layouts of their own invention. The obvious implication of this was that purchasing a typewriter (or typesetter) locked the buyer to a specific manufacturer, because replacement entailed having to learn an all-new layout, with a consequent loss of typing speed when learning the new machine.

The QWERTY layout proved very successful and was adopted by other manufacturers. Some say that the reason why it was so successful is that it actually sped typists down, so that typing machines jammed less frequently. I don’t know if that’s actually true or not, mostly because there are huge issues when researching typing speeds using different layouts. But whatever the case may be, the QWERTY layout and its derivatives are still the single most successful keyboard layouts these days.

Mechanical layout vs Functional layout

Of course, 19th century typewriters are different from computer keyboards: typewriters used to have round keys, whereas computers use square or rectangular keycaps to close a circuit that then sends information to the computer. And of course, typewriters, at least purely mechanical ones, had no Enter key: line breaks were inserted by activating a lever on the right side of the drum that pushed the paper upwards of a previously-chosen number of clicks and sliding the drum itself from right to left. There were no Ctrl or Alt keys. Thus, QWERTY and derivatives are functional layouts: they define what letter should appear on a certain key, but says nothing about how the keys are actually placed on a keyboard. That’s what a mechanical layout is, like ANSI and ISO.

ANSI vs ISO layout

The two layouts are named after the two standardization organizations that codified them: ANSI stands for American National Standards Institute, a US organization that publishes standards that apply to American-, and sometimes also Canadian-, built devices. ISO stands for International Standards Organization, a non-governmental body that oversees and coordinates the national standardisation organizations of its member states. ANSI keyboards are more commonly found in the US, mostly because English doesn’t need that many special characters, like accented or umlauted letters. By contrast, ISO keyboards are predominant in Europe, because many languages there require special characters. The two layouts are mostly similar, but with a few key differences that may turn off users that are forced to use the other layout.

Here are the differences between the two:

  1. The number of keys: standard ANSI keyboards have 104 keys and tenkeyless variants (without a numeric keypad) have 87. ISO keyboards have one additional key, placed next to left Shift;
  2. The shape of the Enter key: ISO keyboards’ Enter key has the shape of a reversed L, whereas ANSI keyboards’ is a normal horizontal key;
  3. The length of the left Shift key: on ISO keyboards, it’s shorter to accommodate for the extra key;
  4. The position of one key: on ANSI keyboards, there’s a key between Backspace and Enter. On ISO keyboards, this key has been moved on the bottom left side of the Enter key.
  5. ISO keyboards have an AltGr key, whereas ANSI keyboards have two Alt keys. This doesn’t affect usage, however, since the behaviour of the right Alt key is determined by the keyboard layout set in the operating system. In the case of a layout not supporting AltGr, Ctrl + Alt may be used.

The two pictures below highlight in red the differences discussed above.

The UK layout. Source: Wikipedia
The US standard layout. Source: Wikipedia
About Andrea Luciano Damico 109 Articles
Andrea Luciano Damico is a freelance translator from Italy. Among his interests are linguistics, technology, video games, and generally being a chill guy. He runs Let's and