FileVault slowdown is overblown on modern Macs

No, not significantly — especially if you have an Apple Silicon MacBook Air.

Modern Macs handle encryption in hardware. The T2 chip (2018+ Intel models) and M-series chips have dedicated AES accelerators that encrypt and decrypt data on the fly with essentially zero performance cost. You won’t notice it in daily use: browsing, editing docs, watching video, even light coding.

The only time you might feel it is during initial encryption — that first few hours when your whole disk gets scrambled. Just let it run overnight. Also, if you’re on an older Intel MacBook Air (pre-2018) without T2, there can be a slight hit during heavy disk writes, like copying large files or