Keyboard profile refers to the profile shapes of each row of keycaps.
A keyboard can be said to be "low profile" or "high profile", depending on its overall height on the table. Often, a low profile keyboard has scissor switches where switch mechanism is small. A reason for lower and flatter profile is more often to save space, especially in the case of laptop keyboards that are made to be as flat as possible. There are also users who prefer the key surface to be low on the table.
The reason for a curved profile is ergonomics: to even out the distance that the fingers have to move for typing on different rows.
There are different variations on profile, explained below.
All keys have the same angled profile, but the keyboard's backplane is curved. Many keyboards with membranes have this, including the IBM Enhanced Keyboard and many rubber dome keyboards from Fujitsu, NMB, Chicony and others.
There are also keyboards with scissor switches with curved backplanes, but they are more unusual.
The space bar often has a convex profile, for use with the thumb, unlike other keys.
The backplane is flat and curvature is achieved by each row having a different profile. Unlike other configurations, a keyboard with contoured keys can not have keys exchanged between rows without making the keyboard profile uneven.
The majority of full-travel keyboards have this configuration.
Most keyboards have four profiles, for the alphanumeric rows and the numeric row, with the function row and space bar row borrowing profile from adjacent rows. The space bar is often higher and convex.
The ISO/IEC 9995-1 standard labels rows alphabetically starting with the Space Bar's row as row A with the next one up as row B, etc. The standard also mandates that rows above the alphanumeric section start with K and that rows below the Space Bar be labelled from Z backwards.
Several manufacturers do use ISO numbering, or just mostly ISO numbering. Other manufacturers label rows in other ways:
|Row \ Vendor||Keys (QWERTY)||Signature Plastics||QWERKeys||WASD Keyboards||Cherry||Leopold||Topre|
|Function row||Esc, F1,F2,...||1 (or 5)||1||4||E||E||E|
|Space bar row||Ctrl,Alt,Space,..||4||4||1||B (A on older keyboards)||B||B|
Most vintage and modern mechanical keyboards have keycaps in what is called "Standard Profile" or "OEM Profile". The profile is used for keycaps with different key mounts and several switch families, including Cherry MX, Alps SKCL/SKCM series and Mitsumi miniature mechanical.
Example keyboards include keyboards made by Costar (such as Filco Majestouch and WASD Keyboards), Das Keyboard (III), iOne, SteelSeries, Chicony, etc. There are also rubber dome keyboards that have this profile, but those usually have a standard key mount and separate sliders over each dome.
Keyboards from Cherry corporation in the G80 and G81 series have contoured keycaps that are somewhat lower than the "standard" profile. Cherry's keys are sharper on the bottom than most other manufacturer's keys.
Modern Cherry keyboards have the same 'B' row profile on the two bottom-most rows, but some vintage Cherry keyboards have the 'A' row profile on the bottom row, which is higher and more angled. All Cherry keyboards with row 'A' are winkeyless, but not vice versa.
QWERKeys's "J series" is a copy of Cherry's profile row E,D,C,B but QWERkeys numbers them 1,2,3,4 from the top.
Signature Plastics DCS profile
Signature Plastics' popular DCS family is mostly profile-compatible with Cherry Corp.'s keys, but not exactly. Most notably, the profile for the bottom two rows (row 4 profile) is angled more than Cherry's row 'B', while being also lower than Cherry's now deprecated row 'A'. This can cause inconsistencies when using modifier keys from an adapter kit made by SP together with Cherry keys on the same row.
Vintage Apple Macintosh
Vintage Apple keyboards (with Alps SKCL/SKCM series or Mitsumi standard mechanical switches) have a completely Apple-specific contoured profile that is not compatible with any other manufacturer. It is almost as if the rows have been moved one step down.
All keys have the same angled profile. The keyboard's backplane is flat and somewhat angled so that the key's surface is (almost) parallel to the desk surface.
This configuration used to be the most common on typewriters, but there are many computer keyboards that have it, both vintage and modern. An example includes the IBM Selectric Touch Keyboard, more commonly known as the "Model M2".
The keyboard's backplane is practically flat on the desk and all keys have the same profile with the key surface facing directly upwards. The exception may be the space bar and other keys on the same row, which could be convex and higher for use with the thumb.
It is common on low-profile keyboards such as those found in laptops.
Also called "island" keys, chiclet keys are flat, and they sit within holes in the upper shell of the keyboard. A few keyboards have a dip in the middle of the keys. It is common for the space bar on a chiclet keyboard to be flat.
The word "chiclet" is an old moniker, from when there was a candy called "Chiclet" which the keys resembled. Early chiclet keyboards (such as the one for the PC jr, Sinclair Spectrum, etc) had calculator-style keys that wobbled when pressed, but modern keyboards have stable scissor switches. However, there are some cheaper modern keyboards that do have low-profile chiclet keys that are not stabilised. The first modern chiclet keyboards were on Sony Vaio laptops, but they were popularized by Apple, and are now found on many new laptops and low-profile keyboards.