How Foreman's Efficiency Mode works, and when to use it

Efficiency Mode in Foreman holds back an app you need open but do not need right now. While that app is in the background, it runs at background priority and is held to about a quarter of the processor time it would take, in short bursts. The moment you bring it to the front, or while it is playing sound, it runs at full speed. This post explains how that works, what it does not do, and which apps suit it.

The problem it is for

Some apps do a lot of work while you are not looking at them. A chat app polls for messages. A browser tab refreshes a page. A video editor finishes a render you do not need yet. You want these open, because closing them means losing your place or your window layout, but they use processor time that you would rather give to whatever is in front of you.

You have two usual choices: quit the app, or live with it. Efficiency Mode is a third. The app stays open and keeps working, but more slowly, until you come back to it. How to stop one app from slowing down everything else on your Mac compares all the options.

How it works, step by step

When you turn Efficiency Mode on for an app, two things happen while the app is in the background.

Background priority. macOS lets a program be marked as background work. The app’s use of the disk is turned down, and on a Mac with Apple silicon its work runs on the efficiency cores, leaving the performance cores for what you are doing. Intel Macs have no efficiency cores, so there the app simply runs at a lower priority than your other work.

Short bursts. On top of that, the app is held to about a quarter of the processor time it would otherwise take. It runs for a short burst, then waits, then runs again. The app is not frozen: it keeps running, just more slowly.

The two work together. Priority decides where and how urgently the app’s work runs, and the bursts limit how much of it there can be.

When it runs at full speed

Efficiency Mode only applies while the app is out of your way. It lifts in two cases.

• In front. When you switch to the app, it runs at full speed until you switch away again.
• Playing sound. While the app plays audio, it runs at full speed. This keeps music, calls and podcasts from stuttering. When the sound stops and the app is in the background, the limit applies again.

In Foreman’s Processes page, a row can read “Efficiency Mode” or “Efficiency Mode, paused while in use”. The second one tells you the limit is lifted for now, while the app is in use.

It is remembered per app

Once you turn Efficiency Mode on for an app, it stays on for that app until you turn it off. If you quit the app and open it again later, the limit applies again. You do not have to set it up every day. It is a setting for that app, not for one session.

Which processes it works on

Efficiency Mode works on any process running under your account. That includes many of macOS’s own background processes, such as Photos analysis (photoanalysisd), Media analysis (mediaanalysisd) and iCloud Drive (bird). It is not available for Foreman itself, for the core parts of macOS such as kernel_task, launchd and WindowServer, or for processes owned by root, a system account or another user: macOS only lets an administrator slow those down, and Foreman does not offer it. The User column shows who owns a process. A few macOS processes, such as nsurlsessiond, trustd, cloudd and cfprefsd, run two copies: one under your account, which can use Efficiency Mode, and one under a system account, which cannot. The User column tells them apart.

Menu bar apps and a few parts of macOS get background priority only, without the bursts.

How to turn it on and off

Select an app in the Processes page and use any of these:

• the Efficiency Mode button in the toolbar
• right-click the app and choose Efficiency Mode
• the Process menu, or Shift-Command-E
• the Performance page, which lists the apps using the most and has Efficiency Mode beside them

Turning it off works from the same places: the toolbar, the right-click menu, the Process menu, the menu bar panel or any page. The app returns to full speed at once.

If Foreman quits, everything goes back to full speed. If Foreman were to crash, a separate watchdog lets the slowed apps go. And when the 24-hour trial ends without a license, Foreman stops reading figures and anything in Efficiency Mode runs at full speed again.

When to use it

Efficiency Mode suits an app that is open for a reason, busy in the background, and not time sensitive. Good candidates:

• a browser with many tabs, when you are working in another app
• a chat or email client that keeps checking for new messages
• a sync or backup app you want to keep going, but not at the cost of your foreground work
• a long job that can finish more slowly, such as an export you will not need for an hour

It helps most when the Mac is under load. How much it helps depends on how busy the Mac is, and no figure applies to every Mac or every app, so be sceptical of anyone who promises one. Try it on the app that bothers you and watch what happens to the Mac.

When not to use it

Skip it for anything where being slow in the background costs you. A render you are waiting on, a download you want finished soon, or a screen recording should run at full speed.

Efficiency Mode is also not Suspend. Suspend freezes an app where it is, using no processor at all, until you choose Resume. How to pause an app on a Mac instead of quitting it explains that option, which suits an app you do not need to run at all for now.

A simple way to try it

1. Open Foreman with Control-Shift-Escape and sort Processes by CPU.
2. Find an app near the top that you do not need right now.
3. Select it and press Efficiency Mode, or Shift-Command-E.
4. Switch to something else. The app’s row in Foreman reads Efficiency Mode while the app is in the background.
5. Switch back to the app when you need it. It runs at full speed until you switch away again.

Foreman is $12 once, works on up to 3 Macs, and is free for 24 hours from the first launch, so you can try this before you decide. It needs macOS 14 Sonoma or later. Efficiency Mode on a Mac: how to slow down a background app covers the idea in general terms.