Since Microchip Technology acquired Atmel, the official source for all AVR software is the Microchip website.
Comprehensive suites supporting both AVR and ARM-based SAM devices.
If you specifically need AVR Studio 4 or 6 for legacy projects, Microchip maintains an "Archives" section. These are often used for older tutorials or low-spec computers that cannot run the newer Visual Studio-based shells. Key Features of the IDE
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