AltGr key

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AltGr (also Alt Graph) is a modifier key found on many computer keyboards (rather than a second Alt key found on US keyboards). It is primarily used to type special characters and symbols that are not widely used in the territory where sold, such as foreign currency symbols, typographic marks and accented letters.^[1] On a typical Windows-compatible PC keyboard, the AltGr key, when present, takes the place of the right-hand Alt key. The key at this location will operate as AltGr if a keyboard layout using AltGr is chosen in the operating system, regardless of what is engraved on the key.^[2] In macOS, the Option key has functions similar to the AltGr key.

The AltGr key is used as an additional Shift key, to provide a third and a fourth (when Shift is also pressed) grapheme for most keys. Most are accented variants of the letters on the keys, but also additional symbols and punctuation marks. Some languages such as Bengali use this key when the number of letters of their alphabet is too large for a standard keyboard. For example, on the US-International keyboard layout, 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)