The Universe of Discourse

Tue, 05 Sep 2023

Mystery of the missing skin tone

Slack, SMS, and other similar applications that display emoji have a skin-tone modifier that adjusts the emoji appearance to one of five skin tones.

For example, there is a generic thumbs-up emoji 👍. Systems may support five variants, which are coded as the thumbs-up followed by one of five “diversity modifier” characters: 👍🏻👍🏼👍🏽👍🏾👍🏿. Depending on your display, you might see a series of five different-toned thumbs-ups, or five generic thumbs-ups each followed by a different skin tone swatch. Or on a monochrome display, you might see stippled versions.

Slack refers to these modifiers as skin-tone-2 through skin-tone-6. What happened to skin-tone-1? It's not used, so I tried to find out why. (Spoiler: I failed.)

Slack and other applications adopted this system direct from Unicode the modifier characters are part of the Unicode emoji standard, called UTS #51. UTS51 defines the five modifiers. The official short names for these are:

        light skin tone
        medium-light skin tone
        medium skin tone
        medium-dark skin tone
        dark skin tone

And the official Unicode character names for the characters are respectively


So this is why Slack has no :skin-tone-1:; already the Unicode standard combines skin types 1 and 2.

“Fitzpatrick” here refers to the Fitzpatrick scale:

The Fitzpatrick scale … is a numerical classification schema for human skin color. It was developed in 1975 by American dermatologist Thomas B. Fitzpatrick as a way to estimate the response of different types of skin to ultraviolet light. It was initially developed on the basis of skin color to measure the correct dose of UVA for PUVA therapy …

The standard cites this document from the Australian Radiation Protection and Nuclear Safety Agency which has a 9-question questionnaire you can use to find out which of the six categories your own skin is in. And it does have six categories, not five. Categories 1 and 2 are the lightest two: Category 1 is the pasty-faced freckled gingers and the people who look like boiled ham. Category 2 is next-lightest and includes yellow-tinted Central European types like me.

(The six categories are accompanied by sample photos of people, and the ARPNSA did a fine job of finding attractive and photogenic models in every category, even the pasty gingers and boiled ham people.)

But why were types 1 and 2 combined? I have not been able to find out. The original draft for UTR #51 was first announced in November 2014, with the diversity modifiers already in their current form. (“… a mechanism using 5 new proposed characters…”) The earliest available archived version of the standard is from the following month and its “diversity” section is substantially the same as the current versions.

I hoped that one of the Unicode mailing lists would have some of the antecedent discussion, and even went so far as to download the entire archives of the Unicode Mail List for offline searching, but I found nothing earlier than the UTR #51 announcement itself, and nothing afterward except discussions about whether the modifiers would apply to 💩 or to 🍺.

Do any of my Gentle Readers have information about this, or suggestions of further exploration?

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