The Apple TV app movie playback test measures battery life by playing back 1080p HD content with display brightness set to 12 clicks from the bottom or 75 per cent. The wireless web test measures battery life by wirelessly browsing 25 popular websites with display brightness set to 12 clicks from the bottom or 75 per cent. Testing conducted by Apple in October 2019 using pre-production 2.3GHz 8-core Intel Core i9–based 16-inch MacBook Pro systems with 16GB of RAM and 1TB SSD.Battery life varies by use and configuration. The Apple TV app movie playback test measures battery life by playing back 1080p HD content with display brightness set to eight clicks from the bottom. Testing conducted by Apple in October 2020 using pre‑production 13-inch MacBook Pro systems with Apple M1 chip, 8GB of RAM and 512GB SSD.1TB = 1 trillion bytes actual formatted capacity less. Intel-based models are available with up to 32GB memory and up to 4TB storage.Testing conducted by Apple in October 2020 using pre‑production MacBook Air systems with Apple M1 chip and 8-core GPU, configured with 8GB of RAM and 512GB SSD.1TB = 1 trillion bytes actual formatted capacity less.