Download Firefox Developer Edition 121.0b9

Get the latest features, fast performance, and the development tools!

Updated: December 10, 2023

Size: 144 MB

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144 MB · December 10, 2023

Firefox%20121.0b9.dmg

Previous versions More »

137.0b5 March 14, 2025 141 MB 137.0b4 March 12, 2025 141 MB 137.0b3 March 09, 2025 141 MB 137.0b2 March 07, 2025 141 MB 137.0b1 March 05, 2025 141 MB 136.0b9 February 23, 2025 140 MB