What is the euro sign for?

The € sign stands for the European currency. Its international currency code is EUR.

How to write it correctly

In English, the sign usually goes before the amount, with no space: “€12.50”.
In French and Spanish it goes after the amount, with a non-breaking space: “12,50 €”. Follow the convention of the language you are writing in.
In a spreadsheet, use the cell’s currency format rather than typing “€” by hand, so calculations keep working.

Pitfalls

The euro sign is not in the same place on every layout: here it is ⌥ Option+E, on French – Numerical it is ⌥ Option+$.
A non-breaking space can be typed too; on this layout: ⌥ Option+Space.

€ on each layout

System	Layout	Key combination
macOS	French – Numerical	`⌥ Option`+`$`
macOS	French	`⌥ Option`+`$`
macOS	Belgian	`⌥ Option`+`$`
macOS	Swiss French	`⌥ Option`+`E`
macOS	Canadian Multilingual (CSA)	`⌥ Option`+`4`
macOS	Canadian French	`⌥ Option`+`⇧ Shift`+`2`
macOS	Spanish	`⌥ Option`+`E`
macOS	Latin American	`⌥ Option`+`E`
macOS	U.S.	`⌥ Option`+`⇧ Shift`+`2`
macOS	ABC	`⌥ Option`+`⇧ Shift`+`2`
macOS	U.S. International – PC	`⌥ Option`+`⇧ Shift`+`2`

Other methods

Character Viewer

Press fn + E (or Control + Command + Space) to open the Character Viewer, search for “€” by name, then double-click it to insert it.

Text replacement

In System Settings › Keyboard › Text Replacements, map a shortcut (for example “;;x”) to the character €: it will be inserted automatically in most apps.

€ technical details

Unicode code point	`U+20AC`
Official Unicode name	EURO SIGN
HTML entity	`€`
CSS	`content: "\20AC";`
JavaScript / JSON	`"\u20AC"`
UTF-8 bytes	`E2 82 AC`
URL encoding	`%E2%82%AC`

The official name comes from the Unicode Character Database (ICU).

How to type € on a Swiss French keyboard