AltGr

AltGr, short for Alternate Graphic, is a modifier key found on many non-US keyboard layouts, particularly European ISO layouts. It is located on the right side of the space bar and is distinct from the left Alt key.

As a modifier, AltGr enables access to additional characters that are not available with the base key or the Shift key alone. When pressed in combination with another key, AltGr typically yields a third-level character or alternate glyph, allowing input of accented letters, currency symbols, and other diacritics depending on the layout.

The concept is standardized in international keyboard schemes. On many keyboards the key is labeled Alt Graph and is used to produce the so-called third level of a key. In environments where AltGr is not present, its functionality is often provided by composing keys or by mapping Right Alt to AltGr in software.

Usage and platform differences: AltGr is common on Windows, Linux, and many non-US keyboard configurations. macOS generally relies on the Option key for similar functionality rather than a dedicated AltGr key. The exact symbols produced by AltGr combinations vary by layout; for example, many European layouts use AltGr to access currency signs, diacritics, and typographic ligatures.