Keycap: # Emoji

The # symbol rendered as a keycap button. Part of the keycap emoji sequence in Unicode, technically composed of the number sign (U+0023), a variation selector, and an enclosing keycap combining character. Added to Emoji 3.0 in 2016, though the underlying # character is one of the oldest in Unicode (3.0, 1999).

This single symbol has more names and identities than any other character in the Unicode standard. Americans call it the "pound sign" (from its use representing weight, derived from Latin *libra pondo*). The British call it "hash" (and reserve "pound" for £). Bell Labs engineers at some point around 1968 called it "octothorpe," possibly naming it after Olympic athlete Jim Thorpe. Musicians call it a "sharp" (though technically ♯ has slanted lines and # has horizontal ones). Programmers see a comment delimiter. And since August 23, 2007, when Chris Messina) tweeted "how do you feel about using # (pound) for groups," the entire world calls it a hashtag.

Messina refused to patent it because he felt hashtags "were born of the internet, and owned by no one." Twitter initially rejected the idea as "too nerdy." It became one of the most powerful organizing tools in human communication history.

The hashtag's role on social media is shifting fast. On Instagram, Adam Mosseri openly stated that hashtags no longer significantly impact reach. Instagram removed the ability to follow hashtags in December 2024 and now recommends 3-5 relevant tags instead of the old 30-hashtag spam strategy. Discovery has moved to keyword SEO in captions.

On X (formerly Twitter), Elon Musk banned hashtags in ads, calling them an "aesthetic nightmare." The platform's algorithm penalizes posts with multiple hashtags by 40%, though 1-2 niche tags still boost engagement by about 21%.

On TikTok, hashtags still matter more than on other platforms because TikTok's discovery algorithm relies heavily on them for content categorization. But even here, the trend is toward fewer, more specific tags.

The #️⃣ emoji itself is rarely used in place of an actual # character. It appears mostly in educational content about hashtags, tech explainers, or retro telephone references ("press # for more options"). Its main value is as a cultural symbol: it represents the concept of tagging, categorization, and the era when putting # before a word could start a movement.

The # symbol's story starts in ancient Rome. The Latin abbreviation *lb* (for libra pondo, meaning "pound weight") was commonly written with a horizontal bar across the top to indicate abbreviation: ℔. Centuries of hasty handwriting morphed ℔ into #. That's how a Roman weight abbreviation became the number sign on your keyboard.

In 1968, when Bell Labs was designing the touch-tone telephone keypad, engineers needed names for the * and # keys. Someone coined "octothorpe" for the # key. "Octo-" clearly refers to the eight points on the symbol. The "-thorpe" part is disputed: one account attributes it to engineer Don Macpherson, who was campaigning to get Jim Thorpe's 1912 Olympic medals returned. Another theory connects it to the Old Norse word for village. Nobody knows for certain, and the word didn't appear in print until 1974.

The symbol sat quietly on telephones and keyboards for four decades until August 23, 2007, when Chris Messina, a product designer, tweeted: "how do you feel about using # (pound) for groups. as in #barcamp [msg]?" He'd borrowed the convention from Internet Relay Chat (IRC), where channels were prefixed with #. Twitter's response? They told him it was "too nerdy for mainstream adoption."

The hashtag went mainstream anyway after users organically adopted it during the 2007 San Diego wildfires. Twitter finally built official hashtag support in 2009. By 2010, every social platform had copied it. By 2017, #MeToo generated 19 million tweets in its first year. By 2020, #BlackLivesMatter produced 48 million tweets in 12 days following George Floyd's murder. A retired abbreviation for Roman pounds had become the most powerful organizing symbol of the internet age.

1. 0Roman abbreviation 'lb' (libra pondo) begins morphing into # through handwriting↗
2. 1968Bell Labs engineers coin 'octothorpe' for the # key on touch-tone phones↗
3. 1978C programming language uses # for preprocessor directives
4. 1999# character included in Unicode 3.0 (U+0023)
5. 2007Chris Messina proposes using # for groups on Twitter (August 23)↗
6. 2009Twitter officially builds hashtag hyperlinking into the platform
7. 2016#️⃣ Keycap Number Sign added to Emoji 3.0↗
8. 2017#MeToo generates 19 million tweets in its first year↗
9. 2020#BlackLivesMatter produces 48 million tweets in 12 days after George Floyd's murder↗
10. 2024Instagram removes hashtag following, signaling the decline of hashtag-based discovery

In the United States, # is the "pound sign" or "number sign." You press pound to continue on every automated phone system. Checks read "Apt #3B." It doubles as a weight abbreviation (5# of flour). This naming convention caused problems when Twitter went global, because...

In the United Kingdom and most of Europe, # is the "hash." "Pound" means £. Telling a British person to "press the pound key" on their phone creates genuine confusion, because the £ symbol isn't on a phone keypad. The transatlantic naming war is unresolvable because both sides have legitimate historical claims.

In music, # is often used as a stand-in for the sharp sign (♯)), though they're technically different characters. The sharp sign has slanted horizontal lines to avoid being confused with staff lines. This approximation gave us C#), Microsoft's programming language, whose name is officially written with the number sign but pronounced "C sharp." The name was a pun: just as C++ increments C, C# (looking like four + signs in a grid) was meant to increment C++.

In programming, # serves as the comment delimiter) in Python, Ruby, Bash, Perl, and YAML. Millions of lines of code start with # followed by a human-readable note. It's also the preprocessor directive prefix in C/C++.

And in social activism, the hashtag became arguably the most powerful organizing tool of the 2010s. #BlackLivesMatter has been used over 44 million times on Twitter. #MeToo appeared in 46 languages within its first year. 69% of Americans believe social media is important for getting politicians to pay attention to issues.

• •Chris Messina proposed the hashtag on August 23, 2007), borrowing from IRC channel naming. Twitter told him it was 'too nerdy for mainstream adoption.' He refused to patent it, saying it belonged to the internet. The hashtag went on to power social movements, marketing campaigns, and the entire content discovery model of the 2010s.
• •#BlackLivesMatter was tweeted 48 million times in just 12 days following George Floyd's murder (May 26 - June 7, 2020). The total lifetime count exceeded 44 million unique tweets from 10 million users. 72% expressed support for the movement.
• •The word 'octothorpe' was coined at Bell Labs around 1968 for the # key on touch-tone phones. The '-thorpe' part may honor Jim Thorpe, the legendary athlete whose 1912 Olympic medals had been stripped. An engineer involved in naming it was reportedly campaigning for Thorpe's medals to be returned.
• •The # symbol traces back to the Roman abbreviation *lb* (libra pondo) meaning 'pound weight.' Centuries of hasty handwriting turned the ligature ℔ into #. So the 'pound sign' really is about pounds, just not currency pounds.
• •Microsoft's C# programming language is officially written with the number sign (#) rather than the musical sharp (♯)) because standard keyboards don't have a sharp key. The name was a pun: the # looks like four + signs in a grid, implying it's an increment of C++.
• •Instagram removed the ability to follow hashtags in December 2024 and now recommends 3-5 tags instead of the old maximum of 30. Studies found no statistically significant reach difference between posts with and without hashtags. The hashtag went from discovery engine to decorative afterthought.
• •Every language looked at the same eight lines and saw something different. In Swedish it's a *brädgård* (timber yard). In Swiss German it's a Gartenhag (garden fence) or Schweinegatter (pig gate). In Chinese it's 井号 (jǐng hào, "well sign," because it looks like a well mouth). In Brazilian Portuguese it's jogo da velha ("old lady's game," i.e., tic-tac-toe). The French government officially decreed that the word "hashtag" should be replaced with mot-dièse.

• •Using #️⃣ when you mean to type an actual # hashtag will look weird. The emoji renders as a keycap button, not as a text character. Use the actual # for hashtags.
• •Calling # the 'pound sign' in British company will confuse people who think you mean £. Say 'hash' internationally.

• •Chris Messina's 2007 tweet — The tweet that started it all): 'how do you feel about using # (pound) for groups. as in #barcamp [msg]?' Twitter rejected the idea as too nerdy. Messina refused to patent it. It became one of the most consequential suggestions in internet history.
• •#MeToo movement (2017) — Originally coined by activist Tarana Burke in 2006, the hashtag went global when Alyssa Milano tweeted it after the Weinstein allegations. 19 million tweets in year one, 46 languages. The hashtag proved a punctuation mark could reshape power structures.
• •#BlackLivesMatter (2013-present) — Created by Alicia Garza, Patrisse Cullors, and Opal Tometi after Trayvon Martin's killing. Became the largest social movement in US history by some measures: 48 million tweets in 12 days following George Floyd's murder.
• •Bell Labs and the octothorpe (1968) — When Bell Labs designed the touch-tone keypad, engineers needed a name for #. Someone coined 'octothorpe,' possibly honoring Jim Thorpe. The word didn't appear in print until 1974 and is now mainly used by typography enthusiasts trying to seem interesting at parties.
• •C# programming language (2000) — Microsoft named their language C#) as a pun: the # looks like four + signs, implying C# increments C++. It's officially written with # because keyboards don't have ♯. Millions of developers write in a language named after a typographic compromise.
• •'Press pound to continue' (1970s-present) — The phrase that defined automated phone systems for decades. # on the telephone keypad marks the end of input. An entire generation associates this symbol with being stuck in IVR hell, pressing 0 repeatedly to reach a human.
• •Instagram kills hashtag following (2024) — Instagram removed the ability to follow hashtags in December 2024 and shifted to keyword-based discovery. The platform that popularized #instagood (1.8 billion uses) essentially declared the hashtag era over. The recommended tag count went from 30 to 3-5.
• •The pound/hash transatlantic war — Americans call it the pound sign. Brits call it hash and reserve 'pound' for £. Telling a British person to 'press the pound key' on their phone causes confusion because £ isn't on a phone. The naming conflict has no resolution and both sides are technically correct.

• •The #️⃣ emoji is a three-codepoint sequence: U+0023U+0023 (number sign) + U+FE0FU+FE0F (variation selector-16) + U+20E3U+20E3 (combining enclosing keycap). Handle with care in string operations.
• •In most programming languages, # is the comment character (Python, Ruby, Bash, Perl, YAML). In C/C++, it's the preprocessor directive prefix (#include#include, #define#define). In CSS, it's the hex color prefix (#FF5733#FF5733). In Markdown, it's a heading prefix.
• •When parsing social media text, ## followed by alphanumeric characters is a hashtag. But ## alone, #!#! (shebang), and #include#include are not hashtags. Edge cases will haunt you.
• •The keycap emoji sequence uses the combining enclosing keycap character U+20E3U+20E3, which is shared by all keycap emojis (0️⃣ through 9️⃣, *️⃣, and #️⃣).

See the full Emoji Developer Tools guide for regex patterns, encoding helpers, and more.