The error: FileVault encryption shows as started (or shows a percentage) but doesn't progress further, sometimes for hours, on a Mac that otherwise appears to be working normally.
Environment: Any current macOS version.
Why this happens: FileVault encrypts in the background at low priority specifically so it doesn't interfere with normal use — which means heavy concurrent disk activity, a nearly-full disk with little room to work, or the Mac sleeping/losing power during the process can all make it appear stalled when it's actually just proceeding extremely slowly, or was genuinely interrupted.
The fix:
- Check actual progress via Terminal rather than trusting the System Settings percentage alone:
sudo fdesetup status. - Confirm the Mac has adequate free disk space — FileVault needs meaningful headroom to encrypt in place; a nearly-full disk can slow this dramatically.
- Keep the Mac awake and plugged in (disable sleep temporarily) since encryption pauses when the machine sleeps and doesn't always resume promptly.
- If it's been stuck for an unreasonable length of time with zero progress via the status check above (not just slow, actually zero movement), a restart often kicks it back into progressing — the process is designed to resume safely after a restart.
One thing worth knowing: "slow" and "stuck" are genuinely different situations here, and checking real status via Terminal instead of watching the UI percentage is the only reliable way to tell them apart before deciding to intervene.