What is the ‘at sign (@)’?
The ‘at sign’, or ‘at symbol’, hovers above the number two on a standard American keyboard and is a required symbol in the formation of an email address.
It has also become a common mechanism for tagging, or mentioning, specific users on social media tools like Instagram and Twitter (X).
How does the at symbol work with email?
For example, if you wanted to email me, you’d just email cameron@theserverside.com.
If you wanted to mention me in a Microsoft Teams chat, you’d type:
@cameron.mckenzie just wrote the best definition of the at sign you'll ever read.
Similarly, preceding a username or handle of a user on social media tools like TikTok, Twitter (X), Instagram and YouTube will tag and notify that account.
What was the @ symbol used for before the Internet?
Long before the rise of TikTok and email, the @ symbol was used to describe the price of goods.
For example, the sign on a Leamington tomato stand might say:
4 tomatoes @ $0.50 = $2.00
That means four tomatoes at 50 cents each.
This commercial use is important because it explains why the symbol makes so much sense in an email address.
cameron@example.com
literally reads as:
Cameron at example.com.
Who invented the @ symbol for email?
So as you can see, it wasn’t the Internet that invented the @ symbol. The Internet just made it famous after Ray Tomlinson found the perfect technical use for it.
In 1971, Tomlinson was working with ARPANET, the computer network that would eventually help give rise to the modern Internet.
He needed a way to send a message from a user on one computer to a user on another computer.
That created a naming problem.
Tomlinson needed something that could separate:
username
from:
computer-name
He looked at the available characters on his keyboard and chose @.
Why is the at sign (@) useful for email and TikTok?
It was a clever choice for two reasons.
First, @ was not commonly used in people’s names, so there was little chance of confusing the separator with part of a username.
Secondly, the symbol already meant at.
A user was literally:
user @ computer
or:
user at computer
It was one of those decisions that seems obvious after somebody else thinks of it.
That single choice transformed a relatively obscure accounting symbol into an icon of the digital age.
Where did the @ symbol originally come from?
The @ symbol is much older than email.
One early appearance dates to 1345, although that example appears to have been a decorative way of writing the letter A rather than the commercial @ symbol we recognize today.
A more important example comes from 1536.
A Florentine merchant used a symbol resembling @ while discussing the price of wine. This is much closer to the commercial meaning that eventually became standard.
The exact origin of the shape itself is uncertain.
One theory suggests it evolved from the Latin word ad, which can mean at or toward.
Another theory connects it to the French word à, meaning at. A scribe writing quickly could theoretically turn the accent and the letter into a single looping character.
There is no universally accepted answer.
What we do know is that merchants were using @ centuries before programmers put it to work.