Download Firefox Developer Edition 139.0b9

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

Updated: May 18, 2025

Size: 142 MB

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142 MB · May 18, 2025

Firefox%20139.0b9.dmg

Previous versions More »

140.0b3 June 01, 2025 144 MB 140.0b2 May 30, 2025 143 MB 140.0b1 May 28, 2025 144 MB 139.0b10 May 19, 2025 142 MB 139.0b9 May 18, 2025 142 MB 139.0b8 May 16, 2025 142 MB