O Button (blood Type) Emoji

The O button (🅾️) is a white capital O on a red square — the blood type O emoji. Type O is the most common blood type globally (~45% of people) and carries a special medical distinction: O-negative is the universal donor, meaning it can be transfused to anyone regardless of their blood type. That makes O-neg the most valuable blood in emergency rooms — it's what paramedics use when there's no time to test. In Japanese ketsuekigata (blood type personality theory), Type O people are natural-born leaders: confident, optimistic, outgoing, and stubborn. They're the "influencer" type — charismatic but sometimes pushy. On social media, 🅾️ doubles as an exclamation ("🅾️" = "OH!"), a letter for stylized text, and a blood donation reference.

🅾️ gets more non-blood-type usage than 🅰️ because the letter O works as an exclamation. "🅾️H NO" and "🅾️MG" use the red square as emphasis. In East Asian social media, it carries the same ketsuekigata personality weight as the other blood type emojis — dating profiles, personality discussions, and anime character profiles. Blood donation campaigns use 🅾️ to specifically call out O-negative donors since that type is always in short supply. Among the blood type emojis, 🅾️ has the broadest dual use: serious (medical/personality) and playful (exclamation/letter).

Blood types were discovered by Karl Landsteiner in 1901 — he won the Nobel Prize for it in 1930. The ABO system he identified remains the most important blood classification for transfusions. Type O is special: O-negative has no A, B, or Rh antigens on its red blood cells, making it universally compatible. Before blood typing existed, transfusions were essentially gambling with someone's life — about half were fatal. Landsteiner's discovery turned transfusion from a death sentence gamble into a safe medical procedure. The blood type emojis (🅰️🅱️🅾️🆎) were included in original Japanese carrier emoji sets because blood type is that culturally important in Japan. They were standardized in Unicode 6.0 (2010).

Encoded in Unicode 6.0 (2010) as U+1F17E NEGATIVE SQUARED LATIN CAPITAL LETTER O. Part of the Enclosed Alphanumeric Supplement block. Added to Emoji 1.0 in 2015.

Type O carries different weight in medical vs personality contexts. Medically, O-negative is the universal donor — hospitals worldwide prioritize O-neg donations because it's the only type safe for everyone. Only ~7% of people are O-negative, creating chronic shortages. In Japanese personality theory, Type O people are seen as confident leaders and go-getters, but also as arrogant and insensitive. Type O is ~30% of Japan's population but ~45% globally — the most common type on Earth. In the US, Type O-positive is the most needed blood type (~38% of the population).

• •O-negative is the universal donor blood type — safe for anyone, regardless of their ABO or Rh type. Only ~7% of people have it.
• •Karl Landsteiner discovered blood types in 1901 and won the Nobel Prize for it in 1930. Before his work, transfusions had ~50% fatality rates.
• •Type O is the most common blood type globally (~45%), but in Japan it's only ~30% — behind Type A (~40%).
• •In Japanese ketsuekigata, Type O people are the 'leaders' — confident, optimistic, and commanding, but also stubborn and pushy.
• •The blood type emojis were included in original Japanese carrier emoji sets because ketsuekigata references were that common in Japanese mobile messaging.