At Sign (@): Copy It and Find It on Any Keyboard

The quickest check is the keyboard itself: look at where the symbol is actually printed. On the 2 key means US or Spanish; on the apostrophe key means British; on Q means Latin American Spanish.

The US and UK swap is the one that causes most grief, because both are English layouts and people assume they are identical. They are not: British keyboards follow the ISO standard with 105 keys instead of 104, a shorter left Shift, and a dedicated £ key. The @ and the double quote simply trade places, which is why a machine set to the wrong locale produces «"» every time you try to type an email address.

One detail catches people out constantly: what decides the shortcut is the layout configured in the operating system, not the letters printed on the keys. Buy a laptop in one country, set the system language to another, and the two stop matching — the marked key no longer produces the expected symbol. Fixing it takes seconds in the keyboard settings, and is far better than relearning a shortcut that fights your hardware.

It is far older than computing. Late medieval scribes created it as shorthand for the Latin preposition ad, and its use is documented from the 15th and 16th centuries in Florence, Castile, Seville, Aragon, Catalonia and France. It survived the arrival of printing thanks to Renaissance merchants, who used it on invoices to link a quantity of goods to its price per unit.

That commercial habit is where its Spanish name comes from. Merchants associated the mark with the arroba, an Iberian weight unit borrowed from Arabic ar-rubʿ, «a quarter» — a quarter of a quintal, roughly 11.5 kg in Castile. Spanish and Portuguese still call the symbol arroba today, while English settled on the plainer «at sign».

In Brazil the unit never went away: cattle are still traded by the arroba, fixed there at 15 kg of carcass weight, and prices are quoted per @ every day. It is probably the only place where the symbol's original meaning and its modern one coexist in daily use.

Its third life began with social media. Twitter borrowed the character in 2006 to mark a reply to another user, a convention invented by users rather than designed by the platform, and it spread from there to Instagram, TikTok, Slack and practically everything else. The word «handle» for a username exists because of it.

That is a remarkable run for one character: a medieval abbreviation, then a unit of weight, then an address separator, and now a way of pointing at a person. Few marks on the keyboard have been repurposed so many times without ever changing shape.