What is replayd on a Mac, and why is it running?

What is replayd?

It is the service behind ReplayKit, macOS's screen and audio capture. Apps that record or share your screen, or capture system audio, hand the work to replayd. It lives at /usr/libexec/replayd and runs as you.

On our Mac it was running, with 10 MB of memory, during a session where we were recording the screen with the built in screencapture tool. That is what it is for.

Should I worry that replayd is running?

Running does not always mean recording; it can stay in memory after a recording ends. What matters is who is allowed to use it. Check System Settings, Privacy & Security, Screen & System Audio Recording: every app listed there can capture your screen. Remove any you do not recognise. The purple recording icon in the menu bar shows when a capture is active.

Why is replayd using high CPU?

A capture is running: a screen recording, a video call sharing your screen, a streaming app, or a screenshot tool with recording on. Encoding video is real work. Stop the capture and it settles. If it stays high with nothing recording, restarting the Mac clears it.

See it live

Free Mac's System tab ranks every process by processor use and energy impact, once a second, and marks the ones macOS will not let you quit as protected. Removing a recorder properly, permission included, is shown in uninstalling LICEcap; recordings themselves in OBS recordings.

Related: mediaanalysisd high CPU and photoanalysisd.