AltGr key

AltGr (also Alt Graph) is a modifier key found on computer keyboards. It is primarily used to type characters that are used less frequently in the language that the keyboard is designed for, such as foreign currency symbols, typographic marks and accented letters. The AltGr key is used to access a third and a fourth grapheme for most keys. Most are accented variants of the letters on the keys, but some are additional symbols and punctuation marks. For example, when the US-International keyboard mapping is active, the C key can be used to insert four different characters:

• C → c (lowercase — first level)
• ⇧ Shift+C → C (uppercase — second level)
• AltGr+C → © (copyright sign — third level)
• AltGr+⇧ Shift+C → ¢ (cent sign — fourth level)

Some languages, such as Bengali, use this key when the number of letters of their alphabet is too large for a standard keyboard. On keyboard layouts that do not include an AltGr key, such as US keyboards, the key position is labelled as a right-hand Alt key. When a relevant keyboard mapping is chosen in the operating system, this key will function separately as AltGr (despite being marked identically to the left-hand Alt key). In macOS, the Option key has functions similar to the AltGr key.